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Infrared Photography: Imaging in a Different Light

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Creative Experimentation

As a photographer with an art background and an employee of a company with endless gear options, I am always looking for something to give me a fresh perspective on image making.  On our recent trip to the Wedding and Portrait Photographers International Conference+Expo (WPPI) in Las Vegas I took the opportunity to learn more about Infrared photography with the Sony A7s IR modified camera.

 

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Tearing Down the Sony 24-70 f/4 ZA OSS Vario Tessar

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Those of you who read our teardowns know that we commonly are tearing down Canon or Nikon mount lenses. The reasons are pretty simple and it basically comes down to the fact that we have a lot more of those lenses. If we have a lot more it's less of a problem to take a couple out of stock for a teardown. Plus, we're more likely to be doing repairs on them in-house so we need to know the layout. Not to mention, since we spend most of our day inside those lenses, we know our way around them pretty well and don't look to stupid when we do a teardown.

But people who shoot Sony, or Pentax, or micro 4/3 ask us to rip apart their lenses, too. We've avoided doing that because of the above reasons and because we rarely try to repair them. But in the last few months, we've gotten motivated to look inside Sony E mount lenses. Partly it's because we're carrying a lot more of them. Partly it's because repair costs on Sony lenses have become — well I like Sony, so let's just say "fully valued."

A few days ago, we sent a Sony 24-70 f/4 ZA OSS  to repair because it made a grinding noise and wouldn't autofocus properly. That kind of thing happens all the time and the repair cost at most manufacturers is $200 to $300. When the service center told this would be an $800 repair, we decided to have them send it back and take a look inside ourselves.

"Self Portrait in a Vario-Tessar". Lensrentals.com, 2015. Call for print prices. 

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Sony FE 35 Match-up: Is More, More?

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Time to trash the adapters?

Sony has just released a new line of full frame FE lenses that will hopefully eliminate the need to use adapters with lenses from other systems.  We just received the  Sony FE 35mm F/1.4 ZA Distagon which has the largest aperture in the lineup and we couldn't wait to have a look at it. Will this replace the petite FE 35mm F/2.8 ZA Sonnar? Probably not for the photographer who enjoys fitting a camera/lens combo in her purse. For the low light lover, bokeh buff, and adapter averse? Let’s find out.

Before I show you fair comparisons of each lens at F/2.8, here are photos taken with each lens at its widest aperture.

Both images were captured on the same camera and tripod setup, so it looks like the Distagon is actually a touch wider even though they are both technically 35mm. Will this make a difference? Not really.

 

Sony FE 35mm F/2.8 ZA Sonnar at F/2.8

Sony FE 35mm F/1.4 ZA Distagon at F/1.4

And now for a better look at those out of focus areas I threw the focus ring all the way to the closest focus. With everything blurred it is easy to notice the variations in color between the two images.  The shape in the highlights is slightly different with a noticeable increase in softness in the 35mm F1.4.

Sony FE 35mm F/2.8 ZA Sonnar at F/2.8

Sony FE 35mm F/1.4 ZA Distagon at F/2.8

Time for the contrast challenge. Here is a mix of light and dark subject matter in bright sunlight. Both lenses seem to handle the situation without obvious aberrations, but the solid background makes it easy to see the vignetting in the 35mm F/2.8.

Sonnar at F/2.8 1/5000 ISO 100

Distagon at F/2.8 1/5000 ISO 100

Another thing to consider with these two lenses is the difference in minimum focusing distance. It's handy to purpose wide angle lenses as macros when possible. The FE 35mm F/2.8 has a minimum focusing distance of 13.8in while the F/1.4 version lets you get as close as 11.76in.  And in my experience, 2 inches can really make a difference.

Sonnar at F/2.8 1/2000 ISO 50

Distagon at F/2.8 1/2000 ISO 50

Okay, onward and upward (literally). Let's take a look at flare. As I have noted, the 35mm f/1.4 has a more buttery quality in the out of focus areas. When put against the sun it doesn't seem to hold together as well as the f/2.8 version, exchanging creamy blur for flatter color and more blown out highlights.

Sonnar at F/2.8 1/5000 ISO 100

Distagon at F/2.8 1/5000 ISO 100

And for the final event, landscape photographers, here are two images shot at f/8 focused at infinity. Again, the vignetting and color in the sky is noticeable. What we really want to know, though, which one is sharper. Right?

Sonnar at F/8 1/500 ISO 100

Distagon at F/8 1/500 ISO 100

This is an interesting comparison. The center of each image is very comparable as shown in the 100% crop. You may notice, however, that the edges of the 35mm F/1.4 lose some clarity. This is especially apparent on the left side of this particular image. This is not a flaw of the lens, but due to the curvature in the field of focus.  It's commonly thought that the wider the aperture, the sharper the lens is stopped down. We have seen in our labs at LensRentals that this is often not the case.  Many lenses made to open as wide as F/1.4 are built with a field of focus pattern that have one or several curves making them less desirable for shooting landscapes or architecture.

Sonnar at F/8 1/500 ISO 100 (100% Center Crop)

Distagon at F/8 1/500 ISO 100 (100% Center Crop)

One last thing to consider when comparing these lenses is the size. The 35mm F1.4 weighs in at 1.39 lbs while the smaller 35mm F/2.8 is only .26 lbs. The weight alone could be a deciding factor.

 

I'm really impressed with the image quality of the Sonnar F/2.8. This lens is tiny, sharp, and half the price of the Distagon F/1.4. Am I a sucker, like many others, for the smooth F/1.4 lowlight capable lens? Definitely. And I will probably use it whenever I am renting. For the consumer looking to purchase, however, the FE 35mm F/2.8 looks like a smart choice.

 

Sarah McAlexander

 

 

Just the Lenses: Sigma 24 f/1.4 Art Comparison

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Most of you know I've been very impressed with Sigma's new Art lenses. Their 35mm f/1.4 Art I still think is the sharpest 35mm prime lens made. The 50mm f/1.4 Art is also superb.

When I heard about the Sigma 24mm f/1.4 Art lens, I had some mixed emotions. I was excited that we might get a 24mm lens of similar quality to their 35mm. But the logical side of me thought that perhaps Sigma had bitten off a bit more than they could chew this time. Designing a wide-aperture 24mm lens is much more difficult than designing a fast 35mm lens. Even the best 24mm f/1.4 lenses (I consider the Canon 24mm f/1.4 L to be the best current offering, although that's arguable) still have distortion, aberrations, and some edge softness.

But when our first five copies of the Sigma 24mm f/1.4 arrived, I swiped them from intake and took them over to the testing lab for a quick look and MTF testing on our optical bench. We already had results from the Canon 24mm f/1.4 L, the Nikon 24mm f/1.4 ED AF-S, and the Rokinon 24mm f/1.4 lenses in our database to compare them to.

MTF Tests

As usual, MTF testing was done for five copies of each lens. Each copy was tested at four rotations (0, 45, 90, and 135 degrees) to give an average MTF across the entire surface of the lens, and the results for each lens then averaged. Prior to MTF testing, all lenses were double-checked on OLAF, our 5-micron pinhole collimated testing machine, to assure they were well-centered. Since the Sigma was the focus of this post, I'll show its MTF curves compared to each of the other 24mm f/1.4 lenses.

Legend for all the MTF graphs

 

 

For those of you who don't speak MTF, I'll summarize a bit. In the center 1/2 of the lens (from 0 to 10mm) the Sigma clearly is more contrasty and has better resolution than even the Canon lens, especially at higher (40 lp/mm and 50 lp/mm) frequencies. In the outer part of the image (from 15mm to 20mm) though, the Canon and Sigma are about the same.  The Sigma is better than the Nikon all the way out to 15mm, but again, in the outer areas there is either no difference or the Nikon is slightly better.

The Rokinon is a rather different lens. It doesn't resolve as well as either the Nikon or the Canon, and not nearly as well as the Sigma in the center of the image. The Rokinon's advantage is that its curves remain flat almost to the very edge of the image circle, and again in this outer 1/4 of the image it is as good as the Sigma, or perhaps a bit better.

What the MTF curves suggest, then, is that Sigma has made the best resolving 24mm lens in the center of the image, but at the outer edges they've run up against the same aberrations and problems that designers of 24mm lenses have always faced, and haven't managed to overcome those.

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Announcing C-4 Precision Optics

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Or, What I Did Over Winter Slow Season

Those of you who read my blog regularly know I'm not a huge fan of sameness. But new lens releases, lately, have tended to have a lot of sameness. Don't get me wrong, there have been some excellent lenses released; marked improvements and refinements have taken place. Other than (arguably) the Canon 11-24 f/4 lens, though, there haven't been a whole lot of exciting new designs that aren't like anything else on the market.

Most of you also know that I'm friends and coworkers with Brian Caldwell (the man who designed the Coastal Optics 60mm Macro, Metabones Speedboosters, and a number of other great optics) and Aaron "The Lens Whisperer" Closz, who I'm certain is the best person in the U.S.  at optically adjusting lenses.

So one day, we all went out to lunch. One beer led to another, and pretty soon we decided what the world needed most was another lens manufacturing company, and we were just the boys to do it. Brian knows everything there is to know about lens design and likes to think outside the box, so he was an obvious choice. Aaron knows everything there is to know about optical testing and adjustment and likes to think outside the box, so he was an obvious choice, too. I write a blog and was paying for all those beers, so that got me included.

 

Next we needed a catchy name. With Caldwell, Closz, and Cicala being the founders, the name was obvious: C-4 Precision Optics. Why C-4 you ask? Well, there are several versions of that. It could be because there was a lot of beer being consumed at lunch and our counting skills had deteriorated. Or it might be that there's a silent 4th partner (there is, actually, but her name doesn't start with a C). Or perhaps we feared that C-3 would lead to a bunch of Star Wars jokes. No wait, I just realized that my name has two C's in it, so that's 4 C's total.

Plus we liked the whole explosives tie-in. The only things cooler than optics are explosives. Unless we had some exploding optics or were making optical explosives or something. So we got a cool logo made, and opened up shop. Then we dropped the cool logo because Brian hated it, and well, it's hard to have a lens designing company without a lens designer.

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Just the Lenses: The Great 200mm Shoot Out

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For those of you who haven't read our 'Just the Lenses' posts before, these take advantage of our Trioptics Imagemaster optical bench to compare lenses from different camera mounts with no camera involved. Why is that different? Because all other forms of testing (DxO, Imatest, or even photography) tests the camera-lens combination. Sensor architecture, micro lenses, in-camera image processing and other things affect those results. A third-party lens on a Canon 5DIII will have different results than the same lens on a Nikon D800 for example.

Our Trioptics Imagemaster MTF Station

Since we're into optics, we like testing just the lenses themselves, eliminating all of those other variables.

The 200mm focal length is one that people use frequently, whether for action photography, long portraiture, or as a short telephoto lens. There are a lot of different ways to get there, too. Most people use a 70-200 zoom lens. A few use a 200mm prime. And if you shoot Canon or Nikon, at least, there are both name brand and third-party options to consider at that focal length. So testing all of the lenses that can shoot at f/2.8 and 200mm for those mounts seemed like a fun idea.

Meet the Contestants

We stock a lot of lenses that can shoot at 200mm and f/2.8 aperture for Canon and Nikon mount cameras:

We tested each of these lenses at f/2.8, 200mm at infinity focus distance (another advantage of the MTF bench is that it tests at infinity, not at 20 feet or so). For each lens we tested 5 copies, and each copy was tested in 4 quadrants. The MTF results were averaged (we ended up with 20 readings for each lens). All lenses were checked for proper centering on OLAF, our 5-micron pinhole collimator prior to being tested.

Checking lens centering on OLAF. Optical adjustment mallet shown on right. 

 

So What Did It Show?

Let's start with the best of the best, the MTF curves of the 200mm f/2.0 lenses tested at f/2.8.

These are both awesomely superb lenses and looking for differences between them is really just hair splitting. The Canon has a bit better resolution in the center, especially at higher frequencies. The Nikon has less astigmatism off axis. Because of the astigmatism difference the Canon has better sagittal resolution in the corners, the Nikon better tangential resolution. But both are just awesomely good.

Next, we'll go to the best of the rest, the 70-200 f/2.8 IS II and 70-200 f/2.8 VR II at 200mm and f/2.8. 

Notice I'm not exactly letting the suspense build up here, am I?

Again, the minor differences are just hair splitting. The Nikon has a tiny bit better high frequency resolution in the center, the Canon is just a tiny bit better in the edges and corners. Not that you could tell any of this in a photograph, the differences are really small. These are widely considered two of the best zoom lenses made and the MTF graphs back that impression up.

Speaking of the best zooms ever made, let's flip the graphs around and (assuming you were going to shoot them at f/2.8) look at how well the MTF curves of the zooms compare with the equally legendary f/2.0 primes. Although let me be clear, there's a lot more to the differences in the prime and zoom lenses than just MTF.

Well, my comments are just stating the obvious. There's a reason people wax poetic about their 200mm f/2.0 lenses. They are spectacular. But the zooms are damn good.

Here's an example of how good, we'll compare the Canon 70-200 f/28 IS II with what was once one of my favorite lenses, the Canon 200mm f/2.8 prime. The MTF graphs will show you why it isn't my favorite anymore; the newer zoom designs are just better than this older prime lens. It's still a good lens, but clearly not as good as the Canon zoom. (Although it may still be a better value, you can get the f/2.8 prime pretty cheap. Not to mention that it's very small and stealthy for a 200mm lens.)

A similar comparison is the Canon IS II with the much less expensive, and still very good Canon 70-200 f/2.8 NON IS lens.

Scroll up and down and you can understand why I liked the 200mm f/2.8 rather than the non IS zoom back when the Non IS zoom was state-of-the-art. But neither can compete with the IS II zoom from a resolution standpoint.

OK, So What About Those Third-Party Zooms?

Glad you asked. Let's compare the Sigma 70-200 f/2.8 OS to the Tamron 70-200 f/2.8 VC first.

This supports what many of you already know; these are both pretty good lenses. Of the two, the Sigma is a bit better tested on the optical bench. This may not agree with what you've heard, but remember this is a pure test of the optics of the lenses. How well the lens autofocuses, the effects of the camera's micro lenses and image processing, and some other factors are also going to influence performance quite a bit. Think of the optical test as 'how good the lens could possibly be', but realize a host of real-world factors are going to also influence 'how good the lens was on this shot'.

Just for comparison sake, let's look at how the Sigma fares against some of the other lenses we've looked at. (Sure, you can scroll back and forth, but this should make things easier.)  First we'll compare the Sigma with the Canon 70-200 f/2.8 IS II; and the Canon is so close to the Nikon 70-200 f/2.8 VR II that you can pretty much extrapolate.

OK, the Sigma isn't quite as good, but it's still really good and a whole lot cheaper. Maybe a better comparison is to the Canon 70-200 f/2.8 NON IS.

I think those two graphs sum it up nicely. The third party lenses aren't as good as the newest Nikon and Canon zooms, but they probably are a bit better than the older models.

A Bit of Overview

A lot of people use their 70-200mm lenses largely at 200mm, so resolution at that focal length is a big factor. But there's a lot more to choosing the proper lens for the task than resolution at 200mm, of course. In reality things like fast and accurate autofocus, especially for sports shooters, is probably more important than absolute resolution.

The cost of 200mm lenses varies greatly and is certainly a big factor when people decide which lens they want. The Canon and Nikon 200mm f/2.0 lenses are nearly $6,000, while their image stabilized 70-200mm f/2.8 zooms are over $2,000.  The Canon 70-200 f/2.8 NON IS is about $1,500, as is the Tamron zoom. The Sigma 70-200 is about $1,200 and the Canon L prime is the bargain of the bunch at about $800.

If one just considers price and resolution then the third party lenses, which are also image stabilized, certainly offer some advantages over the Canon NON IS lens. The Sigma price is more attractive than the Tamron and the Sigma arguably is a sharper lens in the lab. (Again, I emphasize that rapid and accurate autofocus may be more important than absolute resolution at 200mm.)

My opinion, though, is that the extra cost involved in getting the brand-name zoom lens in this category is probably worth it if you can possibly manage it. The Canon and Nikon f2.8 stabilized zooms are amazing optics. The f/2.0 primes, while wonderful lenses and even better optically than the zooms, are priced like the specialty items they are. The third-party lenses and Canon Non IS are cheaper, and probably good enough for many uses. But don't kid yourself; they aren't as good.

Roger Cicala and Aaron Closz

Lensrentals.com

March, 2015

Visit Us At NAB!

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Register by March 27th and Attend for Free

We'll be at the 2015 NAB Show, April 11th-16th. Stop by Booth #C10418 or our table outside of Post | Production World and get our show special: $250 off any rental order of $750 or more. Register using code LV8838 and attend the show for free!

Sign-up for an Invitation and Party with Us

We'll be hosting a private event for our customers during NAB week (details TBA). If you're attending please let us know and sign-up for an invitation. We'd love to spend time with you!

Party With Us at NAB!

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A Quick Zoom Variation Demonstration

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Sometimes I put up posts basically because I find myself answering the same email over-and-over. One of the emails I get a lot is: "I want the best copy of the xxxx zoom lens."

People get irritated because my response is usually something like this: Which focal length do you want the best copy at? The long end, short end, or in the middle? By best copy do you want the highest center MTF, the best corners and edges, or is the middle of the image the most important to you? Or do you want the one with the flattest field? And again, at which focal length do you want whatever is the most important thing to you to be the best at?

Generally, people miss my sarcasm and just respond that they want the best overall lens. I could probably satisfy that request for a prime lens (it would be splitting hair, but it could be done). But there's no way to do it with a zoom; there are just too many variables, and the variables interrelate and counteract each other in complex ways.

So today I thought I'd just put up some pictures and demonstrate how one single variable, field tilt, changes on a given lens at different zoom distances. We chose Canon 70-200 f/2.8 IS II lenses because they are excellent. So you fanboys that want to take this out of context and say Canon 70-200 f/2.8 IS II lenses have tilt variation, trust me, it's less than the zoom you are a fan off. Every zoom lens made is like this.

Field Curvature Examples

All of these lenses had been tested just prior to running these field curvatures both with test-chart photographs and on our MTF optical bench. All of them were optically at least average, if not slightly better than average by my standards, which are quite a bit higher than what the factory standards are (we reject about 5% of lenses that factory service tells us are fine).

The first lens I'll show you was the weakest of the 12 we tested (although I'll mention again, it was still an "average" copy). It looked fine on all of our usual optical tests, but on the optical bench the MTF chart had some detectible astigmatism at 200mm. The field curvatures at 70mm, 120mm, and 200mm zoom lengths show why. There's a bit of field tilt at the wider focal lengths (about normal for most zooms) but at 200mm the tilt becomes more dramatic and the tangential field is much more tilted than the sagittal field.

 

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SLR Magic's 50mm APO HyperPrime Cine T2.1 MTF Tests

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Zeiss 50mm CP.2 and SLRMagic 50mm T2.1

About a year ago, Andrew from SLR Magic came and spent a couple of days in our lab, testing some of the SLR Magic lenses and getting input on improving the optical adjustments on their lenses. At the time Andrew made it clear their company wanted to up their quality and compete with the better lenses on the market. He contacted me a couple of weeks ago to let me know he was sending a copy of their new 50mm APO T2.1 Cine lens for optical bench testing.

During our conversation it became very obvious that Andrew was very comfortable this new lens was going to test very well. You know me, there's nothing I like better than using our optical testing equipment to crush the comfort right out of a manufacturer, so I was pretty eager to take a look at this lens.

While this isn't a review, I will say the SLR Magic lens was mechanically well made with smooth, steady resistance focusing and aperture rings and had a nice compact size. As an apochromatic lens, one of its major advantages is that longitudinal chromatic aberrations are neutralized, so out-of-focus highlights in both the foreground and background remain color-neutral. But this lens is also designed to be high resolution, capable of shooting excellent 6K images, so some MTF testing seemed in order.

 Optical Bench Results

We will compare the SLR Magic 50mm T2.1 with a couple of similar lenses: the Zeiss 50mm T2.1 and the Leica 50mm f/2 APO Summicron-M. While I don't know what the final pricing on the SLR Magic 50mm will be, I assume it be similar to the Zeiss CP.2 (about $4,000) and certainly less than the Leica (over $8,000). Let me note that we tested a single copy of the lens, so I can't make any comments on sample variation.

 

As you can see in the MTF comparison below, the SLR Magic lens definitely is holding its own with the Zeiss 50mm. In the center of the image they are nearly identical at lower frequencies, while the SLR Magic lens is actually a bit better at higher frequencies. The Zeiss holds it's higher frequencies a bit better in the middle 1/3 of the image. The SLR Magic is superior in the absolute edges. (Remember, the 20mm distance from center we show would be at the very edge of 35mm full-frame edge image. If you are shooting a smaller sensor the outer areas of these MTF charts don't matter to you.)

The 50mm Leica Summicron-M f/2.0 is arguably the best 50mm lens we've tested, particularly at higher frequencies. When we compared the SLR Magic to the Leica, the results shocked me a little - not that the Leica was better, but that the SLR Magic lens was actually fairly close to it, except at the higher 40- and 50- line pair/mm frequencies. That's an outstanding performance.

Field Curvature

As long as we had it on the machine, we did field curvature maps of the SLR Magic 50mm, too. They were very nice, with tangential and sagittal fields very similar, as you would expect from the MTF curves. The field curvature demonstrates that this lens is designed to give a nice flat field from edge-to-edge with just a tiny bit of 'mustache' curvature. This particular copy had just a very slight amount of tilt in the field (0.01 degree), which is excellent -- we don't think anyone could notice less than 1 degree in an image.

A Bit of Summary

This is not a lens review but since we are able to do these tests and most reviewers can't I thought them worth putting up. When we met with SLR Magic way back our primary input was on methods to minimize copy-to-copy variation. Testing one copy doesn't give us any insight into the progress they've made there (although I completely agree with the steps they've taken and am optimistic). However, the perfectly flat field with no tilt in this sample gives some evidence that things are looking good. With many lenses almost every single copy has some tilt.

Until final pricing is established there's no way for me to say if this lens is a bargain or not. But assuming the price is reasonable, it certainly provides excellent image quality from an MTF standpoint. Some early reviews indicate the goals of the APO lens in removing color aberrations have also been met. It looks to me like SLR Magic has upped their game quite significantly here.

Roger Cicala and Aaron Closz

Lensrentals.com

March, 2015