The company’s other offerings have all had excellent optics. Construction quality has been rather iffy, and getting one repaired nearly impossible. On the other hand, good optics at prices like they offer makes the build-quality trade off more than acceptable.

I should mention I’m a bit of a Rokinon fan. I own their 14mm because at $379 I think it’s an insane bargain for a very sharp lens. For that price, compared to $2,300 for a Canon 14mm, I’m more than willing to give up autofocus, accept some barrel distortion, and consider it disposable. If it breaks getting a new one won’t be much more expensive than the standard repair cost for a Canon 14mm and less than the repair cost of a Nikon 14-24.

But a tilt-shift is a lot more complex than a simple prime lens, and the RokiBowYang 24mm tilt-shift costs a lot more than their 14mm. So I’ll admit that going in I was a bit skeptical of this lens.

Look and Feel

The first noticeable thing when comparing the Canon 24mm f/3.5 TS-E II, Nikon 24mm PC-E, and Rokinon 24mm TS lenses is the weight.  The Canon weighs in at 780 grams (27.5 ounces), the Samyang at 680, and the Nikon at 730 grams. The Samyang does NOT come with a hood, which the other two have, although they are very shallow hoods that probably aren’t particularly effective.

I think it important to note that the Rokinon has only has 6 aperture blades, compared to 8 for the Canon and 9 for the Nikon. While the Rokinon aperture is round when wide open, stopping down, even a little bit, clearly changes it to a hexagon.

One other thing I noted as soon as I used the lens: the Rokinon has smaller plastic knobs for controlling tilt-shift and locking. The small lever that allows you to rotate the lens on its base and the tilt and shift axis is rather thin plastic (compared to metal on the other lenses) that flexes about 30 degrees when pushed. That makes me a bit nervous; it certainly seems like it could break off without too much pressure.

As far as function, though, the Rokinon gives everything you would ask: 8.5 degrees of tilt, 12 degrees of shift, rotating base and the shift and tilt axis can be rotated so they are aligned or at right angles to each other. The Canon 24mm  TS-E can match all these functions, but the Nikon can’t match the rotations.

Imatest Results

Unfortunately, Imatest results can only be obtained with the lens in straight position, so we can’t compare tilted and shifted. Plenty of lens reviewers will be comparing tilted and shifted images, soon, though.

We tested 4 copies in Canon mount on our Canon 5D Mk II test cameras in the usual fashion. The table below shows the results for the Rokinon versus the Canon 24mm f/3.5 TS-E L. The numbers represent MTF 50 in the center, averaged across the entire lens surface, and the average of the 4 near-corner areas.

	Center	Average	Corner Average
Samyang 24mm f/3.5 TS-E	730	560	455
Canon 24mm TS-E f/3.5	910	775	520
Canon 24-105 f/4 at 24mm	840	690	490

It’s a bit unfair to compare the Rokinon with a $2,000 lens that is widely recognized as one of the sharpest tilt-shifts made, but that’s the most direct comparison. Since most people probably haven’t shot with the Canon 24 TS-E, I included the resolution numbers for the Canon 24-105 f/4 IS just to give a widely known comparison point. Put simply, the Samyang 24 TS-E resolution is adequate – not great but not awful, either.

I thought measurements against the Nikon 24mm PC-E lens might be more even since the Nikon is a much older design that is probably due for a makeover soon. We did our Nikon-mount tests on a D800, so the higher camera resolution would be expected to give significantly higher MTF 50 numbers than the Canon 5D II. (In previous tests we’ve done, the same lens will have an MTF from 15% to 20% higher on a D800 than a 5D II.)

Unfortunately, one of the 4 Nikon-mount Rokinon copies we received was badly decentered, so we only averaged the test results for the other 3 copies, averaged in the table below.

	MTF 50 Center	MTF 50 Average	MTF 50 corner
Samyang 24mm TS	800	640	500
Nikon 24mm PC-E	990	770	490

The Nikon lens clearly resolves a bit better in the center than the Samyang, although in the corner area things are pretty even.

Let’s all remember, though, that these are tilt-shift lenses. Resolution is important, of course, but absolute resolution is not the primary reason we choose a tilt-shift lens, so these tests may be less important than they would be for a standard prime lens. Unfortunately, as I mentioned earlier, our testing tools don’t let us make comparisons with the lenses shifted and tilted — it’s theoretically possible but so many new variables are introduced I wouldn’t trust the results.

The Samyang also falls behind the others on distortion, with 2.3% barrel distortion compared to 1.4% for the Nikon and 0.9% for the Canon.

Stopping Down Aperture

Comparing the lenses stopped down provides some interesting additional information.

The Canon and Nikon tilt-shifts improve only slightly stopped down (for real world purposes the Canon is really identical from f/3.5 to f/8; the Nikon gets a bit sharper in the corners by f/5.6). The Samyang, however, improves quite a bit stopped down.

On the 5D II it never quite catches the Canon lens’s peak resolution, but at f/11 they are identical. (The Canon lens is not getting any sharper from f/8 to f/11, so all we see is diffraction softening. The Samyang is still improving optically, more than enough to offset the diffraction softening.) Compared to the Nikon lens Samyang has almost identical resolution at f/8.

This is a rather important point. A landscape shooter who plans to use tilt function to maximize depth of field and shoot at small apertures should find the Samyang very competitive with the brand name lenses. Someone who plans to shoot at wide apertures will almost certainly notice the difference.

A Very Few Images

Obviously this isn’t a review — I’m a tester not a reviewer. I was able during the few hours it hasn’t been raining this weekend to take a few shots with the lens on a Canon 6D. They may give a little idea about untilted/unshifted image quality and a chance to look at out of focus areas.

Evaluating the out of focus areas, it appears the lens has both longitudinal chromatic and spherical aberration wide open, which is probably why it sharpens up so nicely stopped down. If you want to see 100% jpgs, you can do so HERE.

Conclusions

Obviously this isn’t a full review (that’s not what I do), but hopefully will provide a little information for those considering this lens.

I consider it reasonably priced for the image quality it delivers, but not a screaming bargain by any means. (I consider the RokiBowYang 14mm a screaming bargain.) But, since there is very little competition in the ‘reasonably priced’ tilt-shift lens category, I expect it will sell well.

For those who primarily shoot this kind of lens stopped down, it may be a very good choice. Wide open it’s still acceptable, but the difference between it and the Nikon and Canon versions are going to be noticeable at f/3.5.

I am concerned about the reliability issue, especially given the difficulty in getting RokiBowYang lenses repaired in the U. S. I’ll be tearing one down in the next few days and hopefully looking at the build inside will help alleviate (or confirm) those concerns.

Roger Cicala and Aaron Closz

Lensrentals.com

May, 2013

Since we got a nice bunch of the A1 version lenses in yesterday, we thought it would be worthwhile to do a bit of comparison with the older version. For those who haven’t had the pleasure used the original Sigma 30mm f/1.4 lens, it was something of a love-hate relationship. The original 30mm was small, sharp, and inexpensive; a perfect combination for those shooting a crop sensor camera. Unfortunately, it had the somewhat dubious combination of being rather inaccurate to autofocus, yet extremely difficult to manually focus because of its inaccurate MF ring. There was, perhaps, a bit more copy-to-copy variation than many of us found acceptable.

Sigma’s new version of the 30mm APS-C only lens, would, we hoped, eliminate those negatives. It might even be dramatically better than the original version optically. The original wasn’t a bad lens at all, but the recent Sigma 35mm f/1.4 lens had most of us anticipating something impressive with the new 30mm, too. But before we get to the optics, lets take a look at the two versions.

Tale of the Tape

	30mm EX DC	30mm DC HSM
Elements / Groups	7 / 7	9 / 8
Aperture blades	8	9
Min. Foc. Dist. (ft)	1.3	0.9
Filter size	62	62
weight (oz.)	15	15
Price	$289	$499

So the new lens gives us a new optical formula, an extra aperture blade, and closer minimum focusing distance to go along with a higher, although still reasonable, price tag. It also comes with the much improved outer coating that doesn’t peel off like the one on the original lens and a HSM (hypersonic) motor that should improve AF speed and perhaps accuracy.

After putting the lens on a camera the build difference is immediately apparent. The lens feels more solidly built, particularly the hood. Most immediately apparent, though, is that the manual focus ring turns smoothly and accurately, which is not at all the case with the gritty, jumpy, inaccurate MF ring on the original version. Did I mention I didn’t like the original MF ring? To paraphrase Shakespeare, “I would beat thee, but that would only infect my hand.” The new one, though, is a pleasure to manually focus; smooth and accurate.

Optical Evaluation

I don’t usually put optical formulas and MTF charts in these posts, but I’m going to make an exception today. Because the lenses look so similar on the outside and have such similar names, I think it important to demonstrate how different they are inside. Here are the optical formulas for the two lenses.

I need to mention that we tested these lenses on a Canon 7D. Results would be slightly different on other cameras so please try not to make comparisons to, say, the Sigma 35mm f/1.4 tested on a Canon 5D Mk III. Yes, I know you’re going to anyway, but at least now I can say, “I told you so.”

Anyway, we compared the 8 copies of the 30mm A1 that came in today with 6 copies of the 30mm f/1.4 DC that were on the shelf. As usual, average MTF 50 across the entire lens is plotted on the vertical axis, center MTF 50 on the horizontal, both in Line Pairs / Image Height.

As you can see on the vertical axis, the new version (blue dots) has slightly higher overall (average) resolution, while the older version (red dots) has, perhaps, slightly higher center resolution. (The center difference is pretty minimal and I doubt you could pick it up even pixel-peeping.) The difference away from the center is a bit clearer when presented as a table with corner values included.

	Center MTF 50	Avg MTF 50	Corner MTF 50
Sigma 30mm f/1.4 HSM A1	600	490	340
Sigma 30mm f/1.4 EX DC	605	450	260

The lenses, at f/1.4, are about identical in the center, but the new version is significantly better in the corners.

Let’s look at how that changes as we stop down.

The new version starts of sharper in the corners and the corners steadily improve to f/5.6. The old version starts off softer in the corners and improves less as we stop it down. Its corners peak at f/8, but never get nearly as sharp as the new version does.

Conclusion

Like a lot of people, I was hoping for a crop-sensor version of the Sigma 35mm f/1.4 full-frame lens; an amazingly high-resolution optic. This lens isn’t that good optically. It’s a very nice lens with good resolution and excellent corner performance. If corner performance is important to you this lens is a significant upgrade. If you are more interested in center resolution, than optically it’s not better than the original.

However, I’d still consider this a worthwhile upgrade for a number of reasons. Build quality is far better. The new lens can be accurately focused manually, something that live-view shooters like myself found was difficult to do with the original. I can’t speak for autofocus accuracy yet, but the Sigma USB dock,which now has a release date of early May, will allow us a degree of microfocus adjustment not available with other lenses. The dock is fully compatible with the A1 lens. To me, that’s worth the price of the upgrade right there.

Roger Cicala and Aaron Closz

Lensrentals.com

April, 2013

Unlike the CP.2 lens, the ZE and ZF mount Zeiss 135mm lenses have normal photography housings. The manual focus throw is not nearly as long as with the cinema lens, but it is very smooth and the lens focuses beautifully. With its solid metal housing, the Zeiss weighs in just over 2 pounds compared to 1.65 pounds for the Canon. The Zeiss has a 77mm front element compared to 72mm for the Canon, and 9 aperture blades compared to the Canon’s 8. There’s a bit of price difference, too, with the Zeiss listing for $2,122 and the Canon $989 at the moment.

Imatest Results

We had 8 copies of the ZE 135mm f/2 to test today — not enough to give absolute limits of variation but enough to at least give us a good suggestion. I’ve shown the Imatest MTF 50 results (in Line Pairs / Image Height on a Canon 5D Mk II) at f/2.0 below. As you can see this is a nice, tight grouping of results.

Compared to the average (mean) MTF50 values for the Canon 135mm f/2L, the Zeiss is better wide open across the frame, as shown in the table below. That’s very impressive as the Canon is one of the sharpest lenses around.

	Center MTF 50	Avg MTF 50	Corner MTF 50
Zeiss 135mm f/2	945	840	745
Canon 135mm f/2	800	710	640

As we stop the aperture down, though, the Canon catches up quite quickly. As shown in the graph below, the Zeiss slowly sharpens up steradily through f/5.6 on the Canon 5D II, with the corners reaching their maximum at f/8.

The Canon lens peaks at around the same aperture, but resolution increases to a greater degree as we stop down. By f/5.6 the lenses are virtually equal in resolution.

Summary

The Zeiss 135mm f/2 APO-Sonnar is a superb lens. It has one of the highest resolutions we’ve tested overall and the corners are amazingly good, even wide open. You definitely pay for what you get, though. The Canon 135mm f/2 is a superb lens and while it doesn’t have quite the resolution as the Zeiss wide open, it is less than half the price and autofocuses. (The 135mm f/2 is always on my list of the best value lenses available.)

Possibly in reaction to the Zeiss 135mm hitting the streets, a very widespread rumor has appeared that Sigma will announce a 135mm f/1.8 OS Art Series lens later this year. That’s exciting, but the key word here are ‘rumored’ and ‘announce’. While Sigma is generally fairly quick from announcement to release, that still sounds like a lens that won’t be available until the end of 2013 or early 2014. Assuming the rumors are true.

For video shooters, particularly, this lens is going to be a superb tool. Photographers wanting the very best will be interested, too. The optics are as good as it gets.

Roger Cicala

Lensrentals.com

April, 2013

Comparing the Specs

The Zeiss is a bit pricier than the others lenses in this range, and a bit larger. But you get twice as many aperture blades for your money. Not to mention it has significantly more light transmission. Don’t you wish photo lens makers had to use actual transmission (T) instead of theoretical calculations (f)? Looking at the table you kind of see why the camera makers might rather not.

	Zeiss CP.2	Canon IS II	Nikon VR II	Tamron VC	Sigma OS
Price	$19,900.00	$2,200.00	$2,400.00	$1,499.00	$1,249.00
Weight (lb)	6.2	3.3	3.4	3.2	3.15
Length (in)	9.85	7.8	8.1	7.4	7.8
Aperture blades	18	8	9	9	9
Min. Foc Dist. (ft.)	5	3.9	4.6	4.2	4.6
T#	2.9	3.4	3.3	3.2	3.2

Ok, enough of the silliness. The Zeiss lens is clearly an entirely different beast and while we can mount it to our SLRs that’s not what it’s designed for. That extra money and weight go into making it a true cinema lens with long, smooth focus and zoom gearing. It’s also really parfocal, meaning if you focus on something at 70mm and zoom out to 200mm the object is still in focus. None of the photo lenses are (although budget minded cinematographers desperately want them to be).

Just a Little Bit of Handling

I could go on for some time about how accurately it focuses (it does), how smoothly it zooms (totally true) or how it’s not too heavy to hand hold for a while (a complete lie – it weighs almost as much as a Canon 500 f/4 IS II). This is a lens designed from the ground up to be mounted to a set of rails and focused with a geared follow focus system. It’s perfect for that and built as solidly as any cinema lens we carry.

Cinema lenses, as a rule, are designed differently than photo lenses. Photo lenses are about rapid autofocus, which means rear or inner focusing. That in turn means focus breathing, often to the point of massive changes in focal length when you focus closely. Being parfocal is of little importance for a rapidly autofocusing photo lens. When you zoom from 80 to 150mm if the camera can autofocus in a split second, who cares if it’s still in focus after the move? Not to mention the subject might be moving anyway. Being parfocal is very important for a cinema zoom.

We did a quick parfocal check, comparing it with the Canon 70-200 f/2.8 IS II, which is not parfocal (but actually sort of close to it). We simply set the lenses at 70mm and live view focused on the bush in the center with each lens.

Then zoomed to 200mm and took another image.

Here are 100% crops of the bush at 200mm with the Zeiss on the left, Canon on the right.

We did a quick check for focus breathing, too. I won’t repeat the Canon lens, it breathes significantly and the focal length changes as you zoom close. The Zeiss 70-200 did not focus breath significantly from far to near focusing.

Yes, I Had to Run the Numbers

Absolute resolution, historically, has been far more important for a photo lens sitting in front of a high-resolution sensor than a video lens. Even 4K video is about 8 megapixels, not nearly as resolution sensitive as a 36 megapixel SLR. So when we’ve tested video lenses for resolution compared to photo lenses they’ve historically not held up well. Resolution isn’t their primary focus.

But we thought we’d see if the Zeiss could hold its own against the best 70-200 f2.8 photo zoom we have, the Canon 70-200 f/2.8 IS II. Because the Canon is actually shooting at T3.4, we tested the Zeiss wide open (T2.9) and also stopped down slightly to T4. I’m not going to clutter up the tables with the T4 numbers – this lens is as sharp wide open as it is stopped down, with the exception that the corners get just a tiny bit better at T4.

These are Imatest MTF50 results using a Canon 5D II test camera showing point sharpness at the center, average over the entire lens, and average of the 4 corners.

	Center MTF50	Avg. MTF50	Avg. Corner MTF50
Zeiss@ 70mm	990	775	600
Zeiss@ 135mm	915	675	575
Zeiss@ 200mm	815	575	425
Canon@ 70mm	875	755	575
Canon @ 200mm	840	720	525

Well, as you can see from the table, the Zeiss 70-200 T2.9 takes the idea of video lenses being lower resolution and shows that at the right price point, you really do get it all. At 70mm it’s clearly outresolving the Canon 70-200 f/2.8 IS II. The MTF50 decreases steadily at longer zoom lengths, but even at 200mm it’s still as sharp in the center as the Canon, which is the highest resolving 70-200 zoom we’ve tested. And remember the Canon is working at T3.4 wide open, a half stop slower than the Zeiss.

Let’s keep some perspective – if I were a photographer I wouldn’t be spending this kind of money for a 6-pound 70-200mm zoom because it’s sharper at the wide end. And even shooting 6k video I suspect you’d be hard pressed to detect a huge difference in your footage at 70mm. But now you can have a true cinema lens with long focus and zoom throws, properly geared for follow (and zoom) focus, parfocal and without significant breathing that’s as sharp as any photo lens made.

While $20,000 is sticker shock for my photography colleagues, consider a set of three Cooke Panchro primes covering the same focal length at the same aperture costs $22,000 and doesn’t even approach the Zeiss in resolution. Plus Zeiss lenses don’t tend to spit out focus helicoid collars and require a $600 repair every 3 months like Panchros do.

Roger Cicala and Aaron Closz

Lensrentals.com

April, 2012

BTW – I know what you’re thinking. Yes, I do love my job.

But like a lot of people I viewed Leica’s move to a CMOS sensor, rather than the CCD used in the Leica M9 and Leica M-E cameras, with a bit of trepidation. That 18-megapixel CCD had more resolution than one would expect from an 18-megapixel camera. Despite the sensors many limitations, I was concerned that a ‘modern’ 24-megapixel CMOS sensor might actually be a step backward on the resolution front.

So, while I’m not a reviewer, I am a tester and have access to a nice Imatest lab. It seemed a good idea to compare the MTF50 of the new M Type 240 against the older M9 with the same lenses.

I’m pretty sure I’ll be the only person to do this for one simple reason. The new base on the Leica M makes setting the camera up for Imatest incredibly difficult. It wasn’t easy on the previous Leicas, but setting up the M-240 took around 2 hours at just one focal length.

So what you have here is a comparison of MTF50 using the Leica 50mm f/1.4 Summilux ASPH lens. Since the same lens was used for all three tests and for each, multiple focus bracketed images checked and the sharpest kept, it should give us a nice comparison of differences in the sensors.

For those of you wanting numbers on other lenses, I hope someone checks for you. It won’t be me — the M type 240 is just too difficult to set up. But this should, at least, give us a comparison of system resolution with the same lens between the new M-240 and M9.

Imatest Results

I’ll just give the results as tables with MTF (measured in line pairs / image height) in the center, averaged over 13 points, and averaged in the 4 corners. (Both horizontal and vertical resolution are measured at each point.)  We’ll measure at f/1.4, f/2.8 and f/5.6 for each camera.

Camera	Aperture	Center	Average	Corners
Leica M9	f/1.4	700	610	500
Leica M (Type 240)	f/1.4	740	630	590
Leica M9	f/2.8	1030	850	640
Leica M (Type 240)	f/2.8	1070	860	770
Leica M9	f/5.6	1110	970	790
Leica M (Type 240)	f/5.6	1140	990	860

Conclusion

Well, obviously my initial concerns were incorrect. The new M-240 resolves at least as well (measured by MTF 50) as the M9 did. It probably is just a bit better. I don’t want to split hairs – the differences in the center and overall are pretty small and probably of no, or very little, significance.

The difference in the corners, though, does appear to be approaching significance. (One thing to note, in determining the overall weighted average, the corners count only 25% as much as the center, and half as much as the mid points, so the corner difference gets masked a bit in the ‘average’ number.)

Why would there be a corner improvement larger than the improvement in the center or midpoints? My first guess would be that Leica, those masters of on-sensor microlenses, have improved the microlenses on the new sensor. But that could be entirely wrong.

It might also be that the corners are better with a 50mm lens and won’t be as different at other focal lengths. Or perhaps this camera was just perfectly in tune with this lens. (We only have one right now, so I can’t do a comparison.) Hopefully, someone else will decide that’s worth further investigation.

But for any of you who were, like me, a bit hesitant about the new sensor, it’s really good. Judging by what real reviewers like Steve Huff, Ming Thein, and Sean Reid are saying and showing, this is rather redundant anyway. The images are awesome.

Roger Cicala

Lensrentals.com

April, 2013

Or. . . How I Learned to Appreciate Small Aperture Photography

If you read my blog much, you know I’m a resolution fanatic. I test every new lens for resolution. For personal use, I’ll choose the lens with higher resolution over the one with creamy bokeh every time. When choosing a camera, I have a (yes, I’m ashamed to admit it, but it’s true) strong tendency to want the most megapixels. I’m a resoholic.

Being a resoholic, I’ve always been somewhat fanatical about apertures. Whenever possible I shoot with the lens stopped down at least one stop to wring the maximum sharpness out of my lens. But I’m always careful not to stop down too far because I was taught, soon after I picked up a camera, that if you stopped down too far the dreaded diffraction softening would kick in.

With today’s high-pixel density cameras, that meant f/8 was as far as I would ever stop down. My mental map of aperture sharpness was like the ancient maps of the world – past f/8 there was nothing but the notation Here Thar Be Monsters. Or the equivalent label in Latin or Olde English, just because that makes it seem much cooler.

Go to f/11 and the diffraction monster would come and eat the resolution right out of your photographs. The diffraction monster loves to snack on some tasty resolution. When testing I really never checked past f/5.6 or f/8. That’s where the maximum resolution would be. Any further, and, well, you get it by now.

But I knew there were excellent photographers who shot their landscapes and macros at f/11 or even f/16 because they needed the depth of field. I heard rumors of photographers in far off lands who even actually took photographs at f/22. I considered them sort of like those guys who jump off cliffs in batsuits and fly around for a while before pulling their parachute rip cords. It was fascinating to know people did that, but made me a bit queasy. I was certain the survivors would eventually learn the error of their ways.

But lately, some people like Tim Parkin at Onlandscape.com started opening my eyes (by repeatedly beating on my head). They claimed to be shooting at f/16 and even f/22 with high-pixel-density SLRs, carefully postprocessing their images, and getting very nice detailed results. I shook my head sadly at first, hoping they would come to see the light (pun intended). But then I looked at Tim’s recent article The Diffraction Limit and had to admit, their f/22 images didn’t look bad at all.

So I decided it was time to open the closet door and see just how bad the diffraction monster really was.

Preliminaries

Before we get into all of this, let’s remember we’re looking at two simultaneous events when we stop a lens down. I am not going to get into lengthy discussions of Airy Discs, Raleigh Criteria, and other arguments here. You can read about them elsewhere. This is the simple overview of what’s going on.

• 1) As we narrow the aperture (higher f/number) diffraction occurs which causes some loss of resolution.
• 1a) Smaller pixels are affected more than larger pixels since diffraction causes a spread of the point into a disc. A disc of small size might still fit nicely on a large pixel, but might cover two small pixels. The math is mildly complex, it’s not linear, and I’m not going into it more than that.
• 2) As we narrow the aperture, the lens resolution increases.
• 2a) The increase is different for different lenses.
• 2b) The increase may occur at different rates for the center, middle, and corners of a lens.
• 3) Decreasing aperture is sort of a race between these two effects. When we first stop down, the lens sharpening is greater than the diffraction softening. As we stop down further, lens sharpening slows or stops, but diffraction softening continues.

Some Resolution Testing

I’m not one to really believe what I see in online exampless; given enough postprocessing an online jpg can look pretty sharp if the lens was the bottom of a beer bottle. I want at least a side dish of numbers or some comparative crops with my reviews, thank you.

I decided our current Nikon lineup gave me a great opportunity to look at diffraction effects. By shooting the same lenses on a D700, D3x, and D800 I can look at full-frame sensors with 12, 24.5, and 36 megapixel sensors. That gives linear pixel densities of 118, 168, and 204 pixels per mm, respectively.

I decided to use 50mm lenses because we have 3 choices that are quite different in how they behave at various apertures.  The Zeiss 50mm f/1.4 (the schizoid fiftoid) is very soft and dreamy looking wide open, but becomes razor sharp once stopped down to f/5.6 – it’s like two lenses in one. The Zeiss 50mm f/2 Makro planar is quite sharp even wide open, but seems to maximize it’s center resolution by f/4. The Nikon 50mm f/1.4 G is reasonably sharp wide open, but seems to keep getting sharper the more you stop it down.

So I tested all 3 lenses on all 3 bodies at apertures from wide open to completely stopped down in our Imatest lab.

The Effect of Stopping Down on MTF 50

I started right in the middle of my selections: the Nikon D3x with the very predictable Nikon 50mm f/1.4 G lens. Here are the MTF 50 values in line pairs / image height for the center point, weighted average of 13 points, and average of the 4 corner points. Please note that the plotted average is NOT just the average of center and corners, so if the ‘average’ value is near the center, you know the lens stays fairly sharp in the middle regions, while if it’s nearly as low as the corners the lens falls off rapidly away from the center point.

I have to admit I was a bit shocked. Just as expected, the resolution starts to decrease after f/8, but it doesn’t decrease all that much. Even at f/16 the resolution is still quite a bit higher than it was at f/1.4.

The next step was to see how things look with lower and higher pixel density cameras. So I shot the same lens on a D700 and D800.

I was a bit surprised here, too. I had expected the lower pixel density of the D700 would shift the peak resolution a bit, perhaps to f/11, but that wasn’t the case, although the drop after f/8 did seem less severe.

Things weren’t as different as I expected on the D800, either. The center does seem to peak around f/5.6 with the corners peaking at about f/8, which isn’t surprising. The other cameras show only a slight increase in resolution at the center between f/5.6 and f/8 so it makes sense there would be a bit stronger diffraction effect on the D800. I had really expected more than this. The lens still improves in the corners strongly between f/5.6 and f/8 and the improvement is greater than the diffraction softening.

The message I took away, though, is that diffraction softening is real, it occurs where it is supposed to, but it’s really not as severe as I had thought. Even on the D800 resolution is as high, or higher, at f/16 than it was at f/2.8. At f/11 the resolution is as good, or better, than at f/4. And at both f/11 and f/16 resolution is clearly higher than it was wide open. Perhaps the diffraction monster’s teeth aren’t as long and wicked as I thought.

Some Different Lenses

Diffraction softening is fairly constant, but lens sharpening as the aperture decreases is not. Different lenses behave differently. I compared the Zeiss 50mm f/1.4 and 50mm f/2.0 Makro Planar lenses to the Nikon 50mm f/1.4 G we tested above on all three cameras. In the interest of brevity we’ll just show the graphs for the D3x. The variations for the D800 and D700 were similar to these.

Let’s start with wide open performance. At f/1.4 the ZF f/1.4 lens isn’t as sharp as the Nikon 50mm was, while the ZF 50mm f/2 Makro is sharper at f/2 than either of the other lenses at that aperture. The f/2 Makro has reached maximum center sharpness by f/4 and then slowly loses resolution. The lens doesn’t reach maximum corner sharpness until f/8. The ZF 50mm f/1.4 gets maximum center sharpness at f/5.6 and corners again at f/8 on the D3x. (In the graph above, you can see the Nikon reached maximal sharpness at f/8 for both centers and corners.

The pattern was unchanged on the D800, but on the D700 the two Zeiss lenses center sharpness shifted just a bit to the right – moving to f/5.6 for the 50mm f/2 Makro, with corner sharpness remaining peaked at f/8.

So there is some difference in stopped down behavior with different lenses. Before you ask me to go test this or that, the work has largely been done already at sites like SLRgear.com and Photozone – they show center, corner and edge sharpness at various apertures in their lens reviews.

Yes, I Took Pictures

OK, the numbers surprised me a lot, so I went and did what had to be done. I actually took photographs stopped down to f/16 and even f/22.

Here’s one picture I shot at various apertures (this was on a Canon 6D).

What I saw mirrored what the numbers said I would see. Below are some 100% crops of the white gazebo just off center and some tree trunks near the left edge. I also tried something I was told was possible, but hadn’t really believed. I took the obviously diffraction softened f/22 image and did my best to sharpen it in Photoshop. (By best, I mean about 45 minutes testing different combinations of sharpness and contrast enhancement in 3 layers before getting the results shown below as ‘f/22 sharpened’.)

I haven’t tried this kind of sharpening before and was feeling my way along. I’m sure it would be better with practice (I blacked out the large tree-trunk for example and the image is about 1/3 stop darker than when I started) but still I found the results surprisingly acceptable.

One thing I found very interesting is that I could perform what was basically postprocess abuse on the f/22 image to a degree that would have been impossible with one of the other shots. Below, for example, is the f/2.8 image above processed with exactly the same settings I used on the f/22 image. The center crop, particularly, looks like a ‘find edges’ special effect filter.

I don’t mean to suggest that the postprocessed f/22 image is going to be as good as a nice f/5.6 or f/8 image at all. Rather I’m suggesting it can be improved to a larger degree than they can, making up some of the out-of-camera difference between them.

Does this mean f/16 is my new f/5.6? No, not at all. But I think I may become a lot more aggressive about using f/8 and f/11 when I’m trying for a larger depth of field. I even might use f/16 if absolutely needed. I don’t think I’ll be shooting f/22, though. That’s just a step too far for me.

Roger Cicala

Lensrentals.com

March, 2013

An aside: I’ll be going on vacation for 10 days at the end of this week, shooting with my new camera at my new-found apertures. I don’t expect there will be any more blog posts until late March.

A lot of my posts about lens resolution consist largely of showing the MTF 50 numbers from Imatest or our optical bench. That leads to a lot of questions about what that numerical difference really means, and how much you would notice it in photographs.

My usual response to that has been more numbers: SQF data that shows how large of a print would be required for you to see the difference at close viewing angles. But photographers are visual people and more numbers don’t always seem to answer the question. So I thought we’d try to show what a difference in MTF 50 numbers really looks like.

This is harder than you might think. I’m trying to use your monitor, at 72 dots per inch but with a huge color gamut, to demonstrate the difference you would see in a print at 300 dots per inch but with a smaller color gamut. The most accurate way to do it would be to invite you all over to look at some prints, but that’s not practical.

Today’s Testing

We’ll try something I think will usefully demonstrate what the numbers say and what you can see.

1) I’ll test specific copies of several lenses and give you their MTF50 measured by Imatest.

2) I’ll shoot testing-quality images (measured square, tripod mount, remote release, focus bracketed).

We’ll use ISO 12233 charts with the same lenses and show you 100% crops. It’s certainly the most used, and probably the most sensitive, of the optical charts for testing resolution. This should demonstrate what kind of difference a thorough home tester could see.

Its best feature for our purposes are the 4 crossed resolution charts in each corner, which demonstrate off-axis astigmatism pretty well (horizontal and vertical resolution are obviously different when there’s astigmatism) and let us compare the 4 outer quadrants of the lens.

3) Finally, I’ll send the raw files of some routine photographs taken with the same lenses and camera over to Uwe Steinmueller at Digital Outback Photo. Uwe is an expert post-processor, far better than I, and we’ll see how much difference there is when he’s completed his workflow. (To keep this of reasonable length, Uwe’s article is posted separately HERE.)

One nice side bar: one of the lenses has a slightly soft corner as measured by Imatest, but it’s not obviously decentered. So it will be interesting to see if we can actually detect it outside of Imatest measurebating. I’m guessing not, but I haven’t looked yet, I’m just putting my vote up before I complete the article.

Meet Today’s Contestants

I’m going to play with some Nikon-mount lenses today, mostly because that lets me use the Nikon D800‘s sensor to generate the best resolution we can. We’re going to compare some 35mm lenses: The Sigma 35mm f/1.4; Nikon 35mm f/1.4 G; Nikon 16-35mm f/4 VR at 35mm; and the Nikon 24-120 f/4 VR at 35mm.

Why did I choose these? Well, I’ll tell you.

• The Sigma 35mm f/1.4 is the highest resolving 35mm prime I’ve ever tested.
• The Nikon 35mm f/1.4 G is designed another way with emphasis on things other than wide-open resolution.
• The Nikon 16-35mm f/4 VR is an excellent optic, but is weakest at 35mm where we’ll be testing.
• The  Nikon 24-120mm f/4 VR is another excellent optic, and is at its strongest around 35mm-70mm.

Why did I not choose the Nikon 35mm f/1.8, Zeiss 35mm f/1.4, Rokinon 35mm f/1.4, Schneider Cine-Xenar 35mm, or whatever else you’re going to tell me you wanted to see? Because this isn’t a 35mm lens test. It’s an attempt to use some lenses that I know will generate different MTF 50 charts to see how easily you can actually see (or not see) the difference between them.

I tested one sample of each lens, but, of course, chose them from sets that had been recently lab-tested to be certain they were all reasonably good copies. Even then, I tested a second Nikon 16-35 and Nikon 35mm f/1.4, because fanboys love to scream ‘bad copy’ when their favorite lens doesn’t do quite as well as the others. The second copies were no different, and again, they were selected because they were known to be at least average from a pool of 50 copies.

Let’s Test Some Lenses

First I’ll start with a table showing peak center, weighted average, and average near-corner resolution for each lens. The numbers are MTF 50 in line pairs / image height. I should mention these are not my usual average of 50 copies; these are the specific results for one copy of each lens used in this test. (Each copy was, of course, pretested to make certain it was a good copy compared to our database of known values for each lens.)

Lens	Aperture	Ctr	Lens Avg	Corner Avg
Nikon 16-35mm	f/4	946	715	400
Nikon 16-35mm	f/5.6	969	781	460
Sigma 35mm	f/1.4	973	778	480
Sigma 35mm	f/2.8	1171	961	575
Sigma 35mm	f/4	1218	1016	800
Sigma 35mm	f/5.6	1160	1025	825
Nikon 35mm	f/1.4	740	607	425
Nikon 35mm	f/2.8	1020	830	590
Nikon 35mm	f/4	1065	945	775
Nikon 35mm	f/5.6	1135	985	840
Nikon 24-120mm	f/4	1100	883	460
Nikon 24-120mm	f5.6	1100	930	560

The numbers run together a bit in a large table, so let me summarize a few points:

• Except for the Nikon 35mm f/1.4, all of the lenses are maximally sharp in the center by f/4. The Nikon lenses all sharpen their corners further at f/5.6 compared to f/4,but the Sigma doesn’t, at least not significantly. (See — numbers do have some value for real-world photography.)
• At f/1.4 the Sigma has significantly higher resolution than the Nikon 35mm f/1.4. It’s still a bit higher at f/4 (although I’m not sure that slight difference is significant), and they’re about even at f/5.6.
• The 24-120mm seems to outperform the 16-35mm at 35mm (not shocking, as I mentioned the 16-35 gets a bit weaker right at 35mm).
• At f/4 and f/5.6, the prime lenses are better in the corners than the zooms, but not much different in the center.

It might be simpler to look at one of the charts I generally use for presenting Imatest data. The center MTF 50 is on the horizontal axis, weighted average MTF 50 on the vertical, both in Line Pairs / Image Height. To keep it somewhat simpler I’ve just plotted f/4 (square) and f/5.6 (diamond) data for each lens.

Just looking at center resolution (horizontal axis), I’m fairly certain that at f/4 (squares) I could see a difference between the 16-35 and the Sigma 35mm, but could not see a difference between the Nikon 35mm and the Nikon 24-120mm. I’m not so certain that I could see a difference between the Sigma 35mm and those two Nikon lenses, but think I probably could.

Center Resolution Reality Check

Before I put up more test chart examples, let me graph just center resolution for all of the lenses to simplify things a bit. As always, I know some fanboys are going to spit biscuits about how sharp their Nikon 35mm f/1.4 is wide open. This is a good copy, right at average in test results of the 50+ copies we have in stock. At f/2.8 it’s resolving very well indeed, and its edges and corners are excellent, but it’s not designed to win center resolution championships wide open.

 So let’s look at images of the ISO 12233 chart shots of the lenses shot at f/4. The worst resolves at 945 lp / ih (and worst isn’t a good term, that’s still very, very good resolution). The best resolves at 1220 lp / ih, and the other two just over 1100. Can we see the difference in a test chart shot? Here are 100% crops — to save a little bandwidth I didn’t include the Nikon 35mm f/1.4 image – it’s indistinguishable from the 24-120mm. PLEASE NOTE – the Sigma lens was shot at f/4, just like the other two lenses in this example.

I think this shows pretty well that different numbers (if they’re sufficiently different), are something you can detect with a bit of pixel peeping. But it’s not glaringly obvious.

One thing I suggest you do right now: downsize the image to 50% instead of 100% (which most people suggest as a more reasonable approximation for viewing an actual print). You can probably still see the difference. Now downsize it to 12.5% (about online jpg size). Can you see the difference now? If you can, you need a medication increase.

Now, here are three more center ISO 1223 charts. Before I tell you what they are, see if you can rank them from highest to lowest resolution.

If you said the bottom image is just a bit sharper than the top image, you’ve got good eyes. It is, but just a bit. Both are clearly better than the center image, though, aren’t they?

From top to bottom the crops are: Sigma 35mm at  f/1.4 (973 lp/ih), Nikon 35mm at f/1.4 (740 lp/ih), and Nikon 35mm at f/4 (1065 lp / ih). If you go back to the blue bar graph and look at the numbers, we’re comparing the lowest resolution to a couple of the mid resolution lenses. You can scroll back up and compare these to the others.

So what is my summary at this point? A difference of roughly 20% in MTF 50 in the center of the lens is readily visible in test charts. A difference of 10% is visible but you have to really look closely to see it. When it gets down to someone saying “this lens at 950 line pairs / image height MTF 50 is better than that lens at 900 lp/ih – well, that’s getting silly.

How About a Few Corners?

You might want to scroll back up and look at the computer generated ISO 12233 corner image, just to refresh yourself about what ‘perfect’ would be. With real lenses, we don’t often get close to perfect in the corners. This section will also answer a question I get asked fairly frequently — why don’t I post corner numbers and instead use average lens numbers? The answer is because corners are about a lot more than MTF 50.

Just to refresh, all of our lenses have corner resolution from 400 line pairs / image height wide open.  The Sigma and Nikon 35mm f/1.4 both give near-corner resolution over 800 lp / ih when stopped down. At f/5.6 the 16-35mm and 24-120mm have resolutions of 460 and 560 respectively. So what does that look like? Here are lower left corner images from ISO 12233 shots for a representative sample, and I put the MTF 50 numbers in blue on each sample so you don’t have to look back and forth.

Let’s talk about the real things first, before the ‘gotcha’. I think you can all tell the Nikon 35 at f/5.6 is a bit sharper than the two zooms. My eyes don’t think it’s twice as sharp, which the MTF 50 numbers sort of insinuate it is. I think I can tell the difference between the two zooms, pixel-peeping with this 100% crop. At least I think I can. But it’s a lot closer than I would have expected given the 100 point difference in MTF 50.

But I know what you’re thinking, “What’s up with the 35mm at f/1.4 looking so soft?” If we can hardly tell the difference in the two zooms, shouldn’t the 35mm look about the same as the 16-35 at least?

Well here’s a great example of MTF numbers not telling the whole story. The Nikon 35mm f/1.4G has both longitudinal and lateral chromatic aberration in the corners wide open (look along the edges of the thick square where the lines join it, or the edges of the “5″s). The two f/4 lenses, because they’re f/4, don’t really have these issues so they look better, even though the MTF numbers are roughly the same.

There are other things that affect corners a lot in addition to MTF numbers: coma and other aberrations, distortion (you can fix it in post, but you’ll loose some resolution doing so), vignetting, etc. And finally, I should mention the ISO 12233 chart isn’t quite the corners, although it’s fairly close.

So what is my summary about corners? Well, a big MTF difference is a good thing. Like the numbers suggest, the Nikon 35mm prime at f/5.6 is clearly better than either of the zooms. But in the outer parts of the image, MTF is not the only thing, not by a long shot. A smaller MTF difference, even a 20% (100 lp / ih) difference, may not be a good indicator of  which lens has better corners.

There is another 20% difference in MTF corners, though, that I want to look at. What if the difference is between corners on the same lens? In that case the corners, in theory at least, should have the same vignetting, aberrations, etc.

Demonstrating a Problem

Imatest gives us a lot more numbers than the averages I put in the graphs and that gives us an opportunity for another nice example. The Sigma 35mm f/1.4 we used for this test has an upper left (image) corner that’s a bit softer than the others as shown in the more complete Imatest printout below. (Notice the horizontal / vertical resolutions of 399 / 365 compared to around 500 in the other corners). It’s also a bit softer in the right lower (image) midrange than the other midranges. In other words, it’s very slightly decentered.

The question is whether this slight degree of decentering is really visible? (Trust me, this is slight. A really decentered lens would have areas of resolution under 200 lp/ih and much more astigmatism.) Checking SQF numbers tells me the difference should not be visible in an 8 x 11 print. But is it visible with a bit of pixel peeping?

I don’t think there’s any question the left upper corner softness is noticeable with some pixel-peeping. I’m much less certain how noticeable it will be in a real photograph, particularly given it’s location. But certainly it might be. I did check and the difference between the 4 quadrants was about the same at f/4 and f/5.6 — all were sharper, of course, but there was still a noticeable difference.

This does provide a great demonstration of why I continually harp that checking center resolution is no way to test your lens. This copy of the Sigma lens is outstandingly sharp in the center. Only by comparing the 4 outer quadrants could you possibly tell something is a bit off with this lens. By the way, because I know it will come up in comments, this is something we see commonly in wide-aperture primes of all brands. It’s no more frequent with Sigma than Nikon or Canon.

Summary

There are three kinds of people: those who can count and those who can’t.   – Author Unknown

I’m a geek and spend most of my days testing lens resolution; although mostly to detect copies that are out of sorts. I also test newly released lenses for MTF and resolution, too. Numerical results like Imatest measurements are invaluable for that kind of work. They give us reproducible data that we can use to set standards and compare things.

I think, though, that even just showing images of test charts illustrates some of the limitations these numbers have.

In the center of the lens, where aberrations are minimal, MTF50 correlates pretty well with perceived sharpness as long as we don’t try to split hairs.  A difference of 200 line pairs / image height or roughly 20% is clearly visible. A difference of 100 line pairs / image height or 10% in total resolution is visible but probably requires side-by-side comparison. And that’s in a lab shooting test charts and pixel peeping. I’m interested to see what the difference in photographs is after postprocessing.

In the outer 1/3, though, the numbers are less meaningful. Sure, a big difference in MTF is obvious. But things like vignetting, aberrations, and field curvature may make a much larger difference in how the image looks. It’s nice to know the MTF, but I wouldn’t make a purchase on just that basis, ever.

And, of course, we still haven’t even considered real-world things like exposure, focus accuracy, and vibration. I’ve mentioned before autofocus isn’t nearly accurate enough to make MTF measurements, we require careful live view and even then focus bracket. That and other real-world factors are going to have a huge influence on images above and beyond any MTF differences.

Uwe has a follow up with some actual images shot with theses lenses, properly postprocessed from raw files on his website in the follow up article, Seeing the Numbers with Real World Images.

Then, perhaps, I’ll reevaluate our testing and see if other numbers beside MTF 50 might give more information when we evaluate lenses. That seems to be the standard among those who test lenses, although I’ve not seen good proof of why it’s the best number.

Roger Cicala and Aaron Closz

Lensrentals.com

February, 2013

I don’t own an SLR – I go check one out for ‘testing’ when I need one. But I’ve moved out to the country and I want a camera at the house. I can’t really justify to management that I need to test a camera and some lenses for a year or two.

I know what I want: the Canon T4i‘s touch screen, the Canon 6D‘s Wi-Fi, and the Canon 5D Mk III‘s autofocus built around the Nikon D800E sensor, Nikon’s flash system, Pentax’s user interface (I’d take their sensor too, if I went crop frame), and be able to mount lenses from all manufacturers. But given a far-less-than-unlimited budget, I’ll be making some compromises, like everyone else. In order to make comparisons, I want to take a look at exactly how some systems differ.

Most of that doesn’t involve geek stuff like this, but geek stuff is what I know best so that’s where I’ll start. Resolution isn’t the end-all point for deciding on a camera system. It isn’t even the most important point in my decision about a camera system, and I’m a resolution nut. But it is a thing I want to know about.

A Resolution Comparison

One of the things I constantly harp on is that people should not compare Imatest or DxO results on two different cameras. You can’t look at the results of a lens on a crop sensor and a full-frame, for example. You can’t look at results of a lens test on a Canon 5D and make good predictions of how it will behave on a Canon 5D Mk III. We’ve even found lately that you can’t take the results on a Sony NEX-7 and extrapolate to a Sony NEX-6.

But there is one thing you can do fairly reasonably. You can compare two systems (camera and lens) to each other and determine the overall resolution of each system. I had some pretty self-centered reasons for doing just that. I, the ultimate camera system commitophobe, am going to have to buy, with my own money, a camera system. I hate when that happens.

One of the first compromise questions I had involves shooting with 24-70mm f/2.8 lenses; this is my most commonly used lens. The highest resolving 24-70mm f/2.8 lens is the Canon 24-70 f/2.8L II. The highest resolving camera is the Nikon D800E. Since I can’t mount the best lens to the best camera, I thought I’d look into how the two systems compare in final resolution.

I was fairly certain the D800E with a good Nikon lens is going to be better than the 5D Mk III with the great Canon lens. But I wasn’t sure by how much. The other nice thing about working at this focal length is we have a similar lens we can mount to either camera, the Tamron 24-70 f/2.8 VC, to get a little further comparison.

Let’s Look at Just the Lenses

Before we begin, I know there are some Fanboys somewhere who have stopped payment on their reality check and are stabbing pins in their Roger Effigy Doll because I said the Canon 24-70 II is the highest resolving f/2.8 lens. So let’s take the camera out of the equation and compare just the lenses on our Well’s Optical Bench. This means no camera mount, just evaluating the lens itself.

The following are MTF vs frequency plots for the center of the lenses in question – again, this is not Imatest data using camera images, this is purely assessment of the lenses (at infinity focus). The separation of the two graph lines shows the astigmatism of the lens. Almost all lenses have some; the Canon is truly unique in having so little. (These graphs courtesy of Aaron Closz who still gets nervous when I play with the optical bench. It’s nice and predictable, though. If I want him to run some tests all I have to do is sit down and say, “where’s that 70 micron reticle?” and here’s there like magic.)

From direct comparisons we’ve known the Canon 24-70 II had a higher MTF 50 than the Tamron on Canon cameras, and that the Tamron was nearly as good as the Nikon on Nikon cameras. The optical bench shows a bit more differentiation between the Nikon and the Tamron than I expected, but otherwise clearly demonstrates what we already knew. I should mention we tested 2 copies of each, all of which had already been tested using Imatest and shown to be good copies.

System Testing

Now let’s add the camera systems into the mix, something Imatest is perfectly set up to do. We’re going to measure Imatest MTF in line pairs / image height, as always. Since the D800E has 4912 pixels of image height compared to the Canon 5D III’s 3840 pixels the Nikon should resolve somewhere around 1.2 to 1.3 X the Canon’s resolution if the lenses were equal. (Several other factors, including that the Nikon does not have an AA filter, lenses aren’t perfect, and the math is more complex than a simple ratio, make this a very rough estimate.)

Let’s start by comparing the Tamron 24-70 f/2.8 VC on the two different cameras. We shot two copies on two bodies and averaged the results (which, btw, were nearly identical) to show MTF 50 in the center, averaged across the entire lens, and averaged in the 4 corners at f/2.8 and f/4.

These tests are all done at 50mm. I just didn’t have time to set up at multiple focal lengths and 50mm is a strong area for all 3 lenses. I wanted to compare them at their best.

Tamron 24-70mm f/2.8 VC on Both Cameras

	Center MTF50	Average MTF50	Corner Avg. MTF50
Canon 5DIII f/2.8	810	665	350
Nikon D800e f/2.8	1085	855	445
Canon 5DIII f/4	940	710	445
Nikon D800e f/4	1225	955	560

The MTF50 difference between the two cameras shooting the same lens is quite apparent. The difference is a bit greater in the center and a bit smaller in the corners but it is quite significant – as we knew it would be.

Canon 24-70mm f/2.8 II vs. Nikon 24-70mm f/2.8

Now let’s compare the Canon camera with the Canon 24-70 f/2.8 Mk II to the Nikon camera with the Nikon 24-70 f/2.8 AF-S. The better Canon lens should offset some of the Nikon camera’s superior resolution. That is exactly what happened.

	Center MTF50	Average MTF50	Avg. Corner MTF50
Canon @ f/2.8	1000	860	450
Nikon @ f/2.8	1170	945	500
Canon @ f/4	1060	910	505
Nikon @ f/4	1240	1000	570

The higher resolution of the D800E makes the resolution of the Nikon system superior to the Canon system, although the difference isn’t as great as it was when we compared identical Tamron lenses. No real surprise here. Also not surprising, the Nikon lens is slightly better than the Tamron, although this is fairly close.

The real bottom line here is that there are no losers. The resolution numbers all of these combinations show are nothing short of amazing. For example, all three zooms are equal to, or slightly better than, the superb Zeiss 50mm f/2 Makro Planar at equal apertures on the same camera.

I’ll show the f/2.8 data as our usual graph with center resolution on the horizontal axis, average on thevertical, all in line pairs / image height. I think this shows fairly well the actual resolution difference between the cameras (compare the two Tamron results) and the degree to which a better lens closes the gap.

MTF50 (LP/IH) at f/2.8

There’s one other aside that is probably worth mentioning; the test fairly well confirms common wisdom. If we run SQF numbers on these resolution differences, it suggests we’d need a print size of about 11 X 16 to detect this resolution difference. At that print size we should be able to tell the Tamron mounted to 5DIII (worst performer) from the Nikon 24-70 f/2.8 on D800E (best performer) pretty clearly. We might detect the difference between the Canon 24-70 Mk II on the 5DIII and the Nikon on the D800e. On a 16 X 20 print the Canon – Nikon difference would probably be clearly apparent.

So What Did I Learn Today?

Not too much. Like everyone else I already knew the D800E with a good lens was going to out-resolve the 5D III with a great lens, but that I’d need a reasonably large print to see the difference.

It also demonstrates another thing I mention a lot: the value of any third party lens varies according to what camera you shoot. The resolution difference between the Canon and Tamron 24-70 lenses is greater than that  between the Nikon and Tamron. Right now, the price difference reflects that: the Nikon costs $600 more than the Tamron, the Canon $900.

But if you want to look at it another way, the Tamron on a D800E is about the resolution equal of a Canon Mk II on a 5DIII — a bit sharper in the center, not quite as sharp in the corners, but pretty even. The Tamron-Nikon combination (for a guy like me looking at shelling out some major bucks soon) is $1,000 cheaper than the Canon-Canon system.

Of course, all of those prices are going to settle a bit differently in a couple of months. This is just where they are right now. And resolution is just one factor that goes in to choosing a piece of kit.

As to my ongoing search for which camera system I’m buying into, this just answers one tiny question. I’ve got a lot more research to do. I expect you’ll be reading more about that soon.

Roger Cicala and Aaron Closz

Lensrentals.com

January, 2013

A teleconverter spreads out the light leaving the lens so that only the center portion reaches the sensor. The result is the focal length of the lens seems longer (the image is magnified), but at the cost of reducing the amount of light (effective aperture) of the lens. The Speed Booster compresses the light leaving the lens onto a smaller image circle. This makes the focal length seem shorter and actually increases the amount of light reaching the sensor.

The EF to NEX Speed Booster, for example, changes the effective focal length x 0.71, and increases the maximum aperture by 1 stop. A Canon 50mm f/1.2 lens effectively becomes a 35.5mm f/0.9 NEX lens, for example. Videographers all over the internet were singing Hosannah and laying palm leaves along the path of it’s introduction.

I went into my office, shut the door, and sobbed quietly for a while. Why, you ask? I’ll tell you why. About once a day, we get an email saying somthing like, “I just rented a Canon 5D Mk III and shot video of my daughter’s high-school graduation. My footage doesn’t look anything like Vincent LaForet’s. Obviously the camera was defective and I want my money back.”

This adapter was, I thought, going to result in another 50 emails saying, “I just shot video using a generic 50mm f/2.0 lens I bought on eBay with the Speed Booster adapter and Sony NEX VG20 I rented from you. The footage doesn’t look anything like the footage shot with a Zeiss 35mm T1.5 Super Speed shot on a RED Epic. Obviously the equipment is defective and I want my money back.” I know, like I know the sun is going to rise in the east tomorrow, that you don’t put some more glass between a camera and a lens and get a better image.

But marketing hype will be marketing hype and people who want to believe in magic will believe it – and be disappointed when the magic doesn’t happen.

But Then, There Came a Ray of Hope

Then I flipped over to Metabones’ white paper on the Speed Booster and spit coffee. The primary designer of the adapter is Brian Caldwell. If anyone could make optics do magic, he could. He designed, for example, the Coastal Optics UV-VIS-IR Macro lens, an amazing thing that is the gold standard for forensic macro photography. So I read the white paper carefully and it made perfect sense. The White Paper explained how:

1. The Speed Booster introduces zero (none, nada) spherical aberration, even with an f/0.9 output. That’s amazing. The very complete graphics in the White Paper do show it adds a bit of astigmatism and distortion, though.
2. Where teleconverters magnify lens aberration, a focal reducer would reduce aberations basically because it would shrink them.
3. The adapter is physically smaller than a standard, non-optical EF to NEX adapter.
4. Corner illumination is improved.

After reading the white paper, I became convinced that these things were true. And these are all good things.

There was an additional claim made in the white paper, that MTF (modulation transfer function -  acutance and resolution) was also improved. This one I struggled with. To be blunt, I found this section to be, shall we say, selective, in the comparisons made. I was left with the feeling that it might be using some very specific examples to suggest a general conclusion. The section was a bit more carefully worded than other parts of the white paper, and some information in the graphs, that didn’t quite agree with the claim, was downplayed in the text of the section.

I was willing, however, to be convinced that an FX lens mounted to the Speed Booster would have better corner resolution mounted to a Micro 4/3 than the same lens mounted to a full-frame camera – after all, those Micro 4/3 corners are a lot closer to the center of the image. And that it may, or may not, have better corner resolution mounted to an NEX camera compared to a full-frame camera.

So after my research, my impression was this will be, at least a very useful tool. It may be nearly as good as people hope it will be. In other words, it will, like all other imaging gear ever made, follow Roger’s Law of New Product Introduction (pathway A).

Let’s Do Some Testing Boys and Girls!

OK, first and foremost, this is not going to be a bunch of video samples. That’s not what I do. I’m a testing geek that writes words and makes graphs. But for those who have bravely come this far without a picture to ease the heavy burden of reading, let’s have a look at the Metabones Speed Booster.

It’s a nice looking bit of kit – solidly made and well put together. There’s a solid mount for tripods or shoulder mounts underneath. It mounts with a most satisfying thunk and clamps tightly to camera and lens. The optics are close to the surface, though, and some care in handling will be necessary to make sure they don’t scratch.

Let’s Shoot a Few Test Charts

There are a lot of ways to compare lenses with the Speed Booster and not a lot of time, so I tried to choose things that seemed practical. Or cool. Or both.

Starting with cool, I mounted a Canon 14mm f/2.8 II lens, which with the adapter should give us the equivalent of a 10mm f/2.0 NEX lens. That sounds cool to me. Plus I thought we should look at things as extreme as people are likely to get.

We’ll start by comparing simple shots of an ISO1223 chart shot with the lens on a plain adapter and on the Speed Booster. To even things up I moved my position so that the chart filled the image each time, so that we could compare resolution directly. First an overall picture of the chart, followed by center and near corner crops with each adapter.

Canon 14mm f/2.8

Again, the images were from different distances so that the chart filled the image with both shots. It’s not an optically critical test, but I’d call it a complete success for the Speed Booster. Even spotting the original image 1 stop of light, there’s no significant difference in resolution to my eye.

The change in perspective is impressive. These are shot from the same location with the Canon 14mm f/2.8 mounted to a straightforward adapter first and the Speed Booster second.

Canon 50mm f/1.2

That was pretty impressive, now lets stress things a little bit more. The Canon 50mm f/1.2 lens brings a few aberrations to the table and with the adapter will be an f/0.9 equivalent. I can’t think of anything that would stress an adapter more than f/0.9. Again, I’ll reposition myself so both shots fill the frame with the chart. We’ll compare the 50mm f/1.2 on top to the Speedboosted 35.5mm f/0.9 below.

Again, these are not critical tests, but are carefully lined up, best focus of several shots. And again, the Speed Booster comes out very well.  It may be the illumination boost but the acutance in the center, at least seems a little better with the Speed Booster. I would draw your attention, though, to the difference between vertical and horizontal lines in the corner crop of the Speed Booster image. That’s not an artifact of the shot or alignment. With this lens and camera, at least, the astigmatism seems to be showing up a bit. I also note that the image looks oversharpened, but it’s an unsharpened JPEG and this appearance was consistent on multiple shots.

 Canon 135 f/2.0

I wanted to try the other extreme, and made the assumption that this would be about the longest focal length people would want to use the Speed Booster with. I may be wrong about that, but was running out of time today.

Again, if there’s any deterioration in image quality with the Speed Booster, even though it’s a stop of aperture wider, I’m having difficulty seeing it. I also don’t notice the astigmatism with this combination.

But let’s test the resolution a bit more critically.

Imatest results

We don’t have multiple copies of the Speed Booster yet, so this is what we did. We took a Canon 50mm f/1.2 lens and tested it on a Canon 5D Mk II camera. Then we tested that same copy on an NEX-7 using a standard adapter. Finally, we tested those same copies (camera and lens) with our Speed Booster.

Usually when talking about Imatest results I’m sampling dozens of copies and give you the average (mean) resolution in the center and a weighted average of all the test points on the lens. But usually we NEVER test lenses on adapters if we can avoid it. Why? Because even the very best adapter still introduces and extra variation in tilt and centering between the lens and the camera.

Let me word this more carefully because it’s important. When the imaging sensor is placed in the camera, it is carefully lined up to be completely parallel to, and centered with, the lens mount of the front of the camera. A tilt of 20 microns may be visible on a very wide angle lens. A tilt of 40 microns almost certainly will be visible. From repair manuals we know that the sensor can be made parallel  to the lens mount within a few microns so that’s taken care of.

But when the big, heavy lens mount rotates into the big, heavy camera mount, chances are it’s not accurate within a few microns. Let’s assume it’s getting close to the 20 micron limit, because we know with high-quality, wide angle lenses we can often see some side-to-side variation. Sometimes obvious with some pixel peeping, sometimes not at all, but frequently enough that I’ve assumed we’re getting close to tolerance.

This is one of those sources of lens-camera variation I talk about so often. Lens 12345 looks great on camera 54321 but not so great on camera 112233. It may tilt a bit more on that second camera mount.

When we add an adapter we’re adding another heavy duty mount and making it more likely there’s a bit of tilt. It’s rarely apparent (with a high quality adapter) at standard or telephoto ranges, but often can be detected with high resolution wide-angle lenses. It may cause no harm at all. It may create too much tilt. I mention all of this because it’s going to explain some of our test results.

Canon 50mm f/1.2 on a Canon 5D Mk II

On a Canon 5D Mk II and our lens shot at f/1.4, the MTF50 was 590 line pairs / image height in the center; 460 lp / ih averaged over the entire lens, and 265 lp / ih in its worst corner with a barrel distortion of 1.2%.

Canon 50mm f/1.2 on a Sony NEX-7

On the NEX-7 with a standard adapter shot at f/1.4, it resolved 625 lp / ih in the center, 485 averaged over the entire lens, and 210 in its worst corner with a barrel distortion of 0.825% (smaller sensor). The difference in the center and overall isn’t surprising – the NEX has a higher pixel density and is using the ‘sweet spot’ from the center of the lens. The fact that the lowest corner is worse is a bit surprising until you see the overall graph of results:

Notice the upper left corner is worse and the upper right better, and that the right side of the image resolves better than the left. The lens, which behaved very nicely on a Canon camera, is tilted when shot on this particular NEX-7 with this particular adapter. So, of course, we went and got another adapter. It tilted the other way. And we were out of time. From experience I can say the center resolution number is going to be accurate, the actual weighted average should be a few points higher and the worst corner about 275 or so rather than 210 (275 is the resolution on the less affected corner).

So it is with adapters. And before you scream that the adapter was bad, it wasn’t. The guys put those adapters on other cameras and lenses later and they were either dead even or tilted another way. It is what it is. Also remember we’re churning MTF 50 numbers. You need a big difference to be able to actually see the difference in a photograph, and an even bigger difference for it to affect video.

Canon 50mm f/1.2 on NEX-7 with Speed Booster

On the NEX-7 with Speed Booster adapter and shot at f/0.9, it resolved 720 lp / ih in the center, 410 averaged over the entire lens and 230 in the worst corner. Stopped down to f/1.3 the MTF 50 increased to 800 center, 510 weighted average, and 300 for the worst corner. As advertised, the MTF 50 increased compared to the same lens on no adapter.

However, barrel distortion increased to 1.9%. Remember, however, this is in effect now a 35mm lens, so that number isn’t as big a jump as you would think at first glance. Just to note, there was no sign of tilt with this adapter on this camera.

One thing to note – there was definitely a bit of astigmatism, with horizontal and vertical resolution quite different along the edges of the lens. One other interesting note – we measured primarily MTF 50 as this is the number we work with most frequently. We also checked the MTF 20 numbers and for these combinations the Speed Booster had a similar effect: slightly improved but with greater astigmatism.

A reminder for everyone again – we had one copy of the adapter to play with and limited time. But I’ll have to admit that it seems the folks at Metabones pulled off what they claimed: with the adapter a lens is wider, faster, and even a bit sharper.

A Few Images

There’s not a lot of photogenic material around the Lensrentals Lab, but how often do I get to shoot with a 35mm f/0.9 lens? I’ve included some 100% crop areas in the corners of the scaled down shots.

Now, to get completely subjective, there’s something about the images as far as photography that I don’t like, but it’s hard for me to put a finger on it. But if you look at the crops there’s a bit of a glow around highlight areas, both in-focus (in Sarah’s shirt) and out of focus (the rubber bands).

My first thought was perhaps shooting on an NEX -7 could be the issue, since we know that camera has had some problems with adapted retrofocus lenses. Shooting with a Canon 50mm f/1.2 may also be the culprit – that lens is, well, different. But we repeated the rubber band shot with an NEX-6 and then with both cameras and a Canon 85 f/1.2 and the Speed Booster. To my eye (and remember I’m a techie, so I don’t do subjective all that well), there’s a real tendency for highlights, in and out of focus, to bloom a bit at the widest apertures. It seems to go away by f/2.0 affective aperture.

I’d also add, for those who plan on using it, that the autofocus worked well as far as accuracy. Eventually. You won’t be catching any moving targets unless they are turtles, though. I doubt this is of great import to many people, though.

Conclusions

I think it was pretty obvious that I came armed for battle, ready to slam this product as some marketing overhype. I was wrong less correct than I might have been. The Speed Booster does what they claimed it would do, much to my shock and surprise. It creates a wider-angle, greater aperture lens while retaining resolution and acutance.

It does increase astigmatism a bit, although I doubt this will cause anyone problems unless someone is trying to shoot landscape photography with it. It also seems to create some highlight blooming at very wide apertures. Again, nothing that can’t be worked around and probably not something that will be noticeable with anything but the widest aperture lenses.

It is going to take a while and a lot of people experimenting before we find out what combinations of lenses and cameras are awesome with it, which are fairly good, and which fairly bad. They won’t all be the same. But I suspect most of them are going to be pretty good. And this is going to be a very useful tool. 

Most of the little foibles I’ve seen (including the part about adapter tilt) really only apply to photographers trying to tweek every drop of resolution out of their high-resolution sensor. Video, even 5k video, is more forgiving of a slightly weak corner or a bit of astigmatism.

Roger Cicala

Lensrentals.com

January, 2013

The Players

The Canon 24-70 f/4 IS fits in the ‘standard zoom’ lens category which is fairly crowded. The new Canon 24-70 f/2.8 Mk II and Tamron 24-70 f/2.8 VC lenses are already out. The Canon 24-70 f/2.8 Mk I is no longer produced but is in a lot of photographers’ bags already. The Canon 24-105 f/4 IS already offers an f/4 image stabilized zoom with a greater range. It’s a lot to choose from and the new lens is going to have to be impressive to sell well at its higher price.

Let’s take a look at how this group prices out (these are today’s retail prices, but I expect you can get $100 or so off each of them fairly soon).

Lens	Price
Canon 24-70 f/2.8 Mk II	$2,199
Canon 24-70 f/4 IS	$1,499
Tamron 24-70 f/2.8 VC	$1299
Canon 24-105 f/4 IS	$1,091

We’ve previously compared the Mk and Mk II Canons in depth, and compared them to the Tamron f/2.8 VC. A couple of conclusions are already apparent:

• If you want the best 24-70 f/2.8 zoom at any price, the Canon 24-70mm f/2.8 Mk II outresolves anything else, period.
• If you want image stabilization with your 24-70 zoom, the Tamron is really very good, and while it doesn’t quite resolve up to Mk II standards, it does outresolve the Mk I version (which is itself a pretty good lens, at least when you get a good copy).
• The Canon 24-105 f/4 IS gives good quality and greater range at a lower price.

I try to identify my expectations going into an evaluation. In this case, given the price, the 24-70 f/4 IS will need to be a better lens than the Canon 24-105 and at least as good as the Tamron at f/4 to justify its price. I’ll go further and say it should be better than the Canon 24-70 f/2.8 Mk I at f/4 as well. Anything less would be a failure.

The Usual Disclaimer

This isn’t a lens review. I am not a reviewer. I don’t spend days evaluating a single copy of a lens for all of its traits and characteristics, nor do I take hundreds of really great photos with it and describe how it works in the field. Several of the lenses I tested today are on the way to people who will do just that and their thorough reviews will be available in a week or so.

What I do is test multiple copies of the lens for resolution and other basic stuff. Multiple copies lets us take sample variation into account to some degree, which a thorough review of a single lens can’t.

A Quick Comparison

Compared to the Canon and Tamron 24-70 f/2.8 lenses, the new one is a bit smaller at 3.7″ long, 1.32 pounds, with a 77mm front filter ring.

It’s also significantly shorter than the 24-105 f/4 IS – although they actually look quite alike. I’ll add that I really, really, really like the pinch cap on the new lens, which makes it easy to remove the cap even with the hood mounted.

Macro Mode

Not really part of our usual testing here, but the 24-70 f/4 IS has a special switch that allows it to become a near macro (0.7x) at the expense of losing infinity focus. While I usually think of ‘macro zoom’ as a marketing gimmick (and I’m still not sure about this one), Canon did put their Hybrid IS unit in this lens, just like the one in the Canon 100mm f/2.8 IS L macro lens, so I’ll give this one the benefit of the doubt.

I find the macro mode and small size nice differentiators that may make this lens a good choice for some photographers if the optics are excellent. I should mention, though, that the macro working distance is quite short — about 2 inches from the front element. Getting it into macro mode is a bit clumsy as you have to hold the switch while rotating the zoom ring. But it’s a nice feature.

Resolution Results

We tested 22 copies of the Canon 24-70 f/4 IS L at 24mm and 70mm using our Imatest lab. We had numbers from testing 100+ copies of the 24-105 f/4 IS already available. We had recently tested all of our 24-70 Mk I, Mk II and Tamron 24-70 f/2.8 VC lenses, but only at f/2.8, so we repeated those tests on 10 known good copies of each at f/4 so we would be able to compare how all the lenses performed at f/4. There was not time to test everything at f/5.6.

Results at f/2.8

The f/2.8 numbers are posted elsewhere, but I’ll repeat them here.  If you’re going to pay more money for an f/2.8 lens, but mostly will shoot at f/4, it’s worthwhile knowing how much resolution you give up at f/2.8. The numbers are Imatest MTF50 values at the cener, averaged at 13 points over the entire lens, and the average of the 4 corner numbers.

Lens	focal length	CenterMTF50	AverageMTF50	Avg. CornerMTF50
Canon 24-70 f/2.8 Mk I	70mm	710	580	360
Canon 24-70 f/2.8 Mk II	70mm	940	810	480
Tamron 24-70 f2.8 VC	70mm	740	660	420
Canon 24-70 f/2.8 Mk I	24mm	730	610	380
Canon 24-70 f/2.8 Mk II	24mm	950	820	510
Tamron 24-70 f2.8 VC	24mm	815	765	430

The three 24-70 f/2.8 zoons are all good lenses, but it’s obvious from a resolution standpoint the Canon Mk II is the best and the Tamron between the Mk I and Mk II results.

Results at f/4

We have 5 lenses to compare at f/4 and I’ve added corner resolution, distortion, and chromatic aberration numberes. To keep all that data organized I’l make separate tables for results at 24mm and 70mm.

We’ll look at 24mm first.

Lens	CenterMTF50	AverageMTF50	AvgCornerMTF50	Barrel Dist.	CA%
Canon 24-70 f/2.8 Mk I	860	735	470	2.0%	.05%
Canon 24-70 f/2.8 Mk II	1010	910	615	2.1%	.05%
Tamron 24-70 f/2.8 VC	940	815	500	2.8%	.04%
Canon 24-70 f/4 IS	950	825	560	1.7%	.05
Canon 24-105 f/4 IS	890	730	480	5%	.06%

The f/2.8 lenses, which are all good at f/2.8, sharpen up even further when stopped down to f/4. The Canon 24-105 f/4 IS accounts itself well here, resolving just as well as the original Canon 24-70 f/2.8 lens, although it does show more barrel distortion than the others. The new 24-70 f/4 IS isn’t quite what I’d hoped (I was hoping it would match the Mk II f/2.8 lens at f/4), but it’s better than the 24-105 or the original 24-70 f/2.8. It’s probably a bit better in the far corners than the Tamron 24-70 f/2.8 VC, but otherwise they’re about dead even.

One thing that is very good on the new lens is the lower barrel distortion, just under 2%. This probably is most noticeable when compared to the 24-105 f/4 IS, which has pretty bad barrel distortion right at 24mm.

Here is the same data when the lenses are shot lenses at 70mm

Lens	Center MNTF50	AverageMTF50	Avg.CornerMTF50	Pinc. Dist.	CA%
Canon 24-70 f/2.8 Mk I	805	645	430	1.3%	.04%
Canon 24-70 f/2.8 Mk II	975	820	580	1.4%	.05%
Tamron 24-70 f/2.8 VC	890	735	510	1.5%	.04%
Canon 24-70 f/4 IS	920	750	525	1%	.05
Canon 24-105 f/4 IS	840	680	470	1.2%	.05%

None of the f/2.8 zooms are quite as sharp at 70mm as they were at 24mm, but the difference is pretty minimal. The 24-105 f/4 IS still does quite well, perhaps a bit better than the original 24-70, although that’s splitting hairs. It should be mentioned, though, that the 24-105 starts to get a tiny bit softer after 80mm – at 70mm we’re in its sweet spot.

The new 24-70 f/4 IS stays in proportion — it’s about the same as the Tamron, not as good as the Canon 24-70 f/2.8 Mk II, but better than the original Canon 24-70 and the 24-105 f/4 IS.

Sample Variation

I’ve graphed the center and average resolution for all 22 copies below.

That’s a nice, tight pattern at 24mm, but at 70mm things are a bit more spread out. There are two outliers at 70mm. Further testing on the worst one shows it is clearly decentered. The not-quite-as-bad one seems to be a bit decentered as well. I will note that I took these two values out when I calculated the averages above since I want those to reflect good copies of the lens.

Twenty-two lenses is a pretty small sample to make further comments. I’ll have more to say when we have seen 60 or 70 copies.

Addendum, January 14: 

After a head’s up from our friends at SLRgear.com and a couple of other users, who saw lower resolution in their copies at 50mm, we went back and retested a couple of dozen 24-70 f/4 IS at 3 focal lengths (24, 50, 70mm) instead of our usual two. (Most, but not all, zooms have lowest resolution at one extreme or the other, so we focus our testing there.)

We did find that 50mm resolution was slightly lower than 70mm for every copy. The center / weighted average at 50mm for the 24-70 f/4 IS was 875 / 700, compared to 920 / 750 at 70mm. Not a huge drop, but it was consistent. This is a bit surprising, but not a total shock. Some wide angle zooms exhibit similar behavior and the dip in resolution isn’t extreme.

One thing that may be important to those of you who shoot around 50mm a lot, though, is that we also tested the Canon 24-70 f/2.8 Mk II and the Tamron 24-70 f/2.8 VR at 50mm. Both of these lenses were as sharp at 50mm as they were at 70mm, at both f/2.8 and f/4.

Conclusions

Obviously this hasn’t told us a thing about autofocus accuracy, bokeh, or a dozen other things that have to be considered when choosing a lens. Just like you, I’ll be waiting for more complete reviews to tell us about that.

On the basis of this information, though, I’m . . .  well, I don’t know what I am. This is a good lens, but I at the price point I’d probably prefer the f/2.8 of the Tamron VC to the new Canon’s f/4. The macro feature is nice and will certainly pull some people towards the Canon.

This is only a sample of 22 copies, but the sample variation at 70mm is a bit bothersome. I don’t feel comfortable making any statements about it, though, until we’ve seen another 40 or 50 copies. This might just be a couple of bad lenses in a small sample.

My bottom line is I sit here thinking the prices need to settle down a bit. If I was considering upgrading to one of these lenses I’d probably hold off a few months and see how the prices change.

Roger Cicala

Lensrentals.com

January, 2013