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Sony A7R: A Rising Tide Lifts All the Boats?

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I have to admit I didn't get too worked up when the Sony A7 and A7R were released. The last time I wrote about Sony it was how there were so few lenses for the NEX system years after introduction. So now we're going to a system requiring a whole new lens mount. Sure the camera's specs were interesting. But the idea of yet another camera body good mostly for shooting lenses on adapters wasn't very exciting. So I planned to ignore it.

But my friends over at Imaging-Resource / SLRGear.com were waxing poetic when they talked about their testing of the A7. Then they started claiming that the lenses were really good, too, and sent me some rather shocking test results. Plus, I will admit when it arrived I kind of liked the look and feel of the camera. It's a very small camera for a full-frame, but with a nice deep grip that felt good in my overly large hands. Sort of a retro appearance. So even though we were a bit backed up, Aaron and I decided to at least run some some preliminary testing in our Imatest lab with the A7R.

Let me be clear - this isn't an A7R review. Think of it more as a screening test to see if I was even interested in looking at it more seriously. For me, the lack of lenses with a newly released camera means going through several adapters and numerous lenses to see if I could make a reasonably useful kit. There are other options out there that would be a lot less trouble. So unless there was something about it to really impress me, I'd just skip it for now. If things were merely good, I wouldn't be interested in looking further.

Results with the 35mm f/2.8 Sony Zeiss Lens

 

We received a reasonable number of A7R cameras in, but only a few copies of the Zeiss 35mm f/2.8 FE lens and none of the 55mm f/1.8 Sony Zeiss Sonnar FE that Rob Murray reviewed with such spectacular results. But what we had was what we had, so we mounted the 35mm FE to the A7R and ran a set of tests. Then we ran them again because when I first saw the results I thought "we had that stopped down somehow, no way it did that at f/2.8". But it did.

To put this in some perspective, I'm going to do something that's not really OK: compare numbers between systems. I don't want to play camera wars, and these aren't extensive comparisons. But I did want to show you why my jaw dropped when I saw the A7R/35mm f/2.8 numbers.

In this case we're comparing very closely matched systems: the Sony A7R and Nikon D800e are both 36 megapixel, no-AA filter cameras and we're processing raw images that (theoretically) have no sharpening or manipulation applied. Even so, please take this with a grain of salt because, well, we're comparing numbers between systems and that adds variables.

Camera Lens Aperture shot MTF50 Center LP/IH MTF50 Avg LP/IH MTF50 Avg Corner Lp/IH
A7R35mm f/2.8 FEf/2.813201175695
A7R35mm f/2.8 FEf/414201190750
D800e35mm f/1.4 Gf/411501020625
D800eZF.2 50mm f/2f/5.612601100660

Just in case you missed that, the Sony A7R with 35mm f/2.8 lens shot at f/2.8 outresolved the Nikon D800e with either the Nikon 35mm f/1.4G shot at f/4 or the Zeiss 50mm f/2 shot at f/5.6. Stopped down to f/4 to even the playing field, the Sony was clearly higher. In fact, the only lens-camera combinations we've seen with that kind of MTF50 is the Zeiss Otus 55mm mounted to a D800e.

That did leave me with a question, though. Is the lens that great? Or is the camera that great? Or is it the combination?

A Few More 35mm Focal Length Tests

Unfortunately, the only other FE mount lens we had was the little variable-aperture kit zoom. It may be a pretty good lens, but I don't test variable aperture kit zooms when I'm trying to decide how good a camera is. You've got to draw the line somewhere.

The next thing I know Aaron has a tray full of adapters and a bunch of lenses. I pointed out that we don't test lenses on adapters. I use adapters for taking pictures, they're wonderful for that. But when you generate test numbers there's always a bit of tilt that makes the overall test numbers lower than they should be. So I told him we absolutely weren't going to test lenses on adapters.

He pointed out that center numbers would still be accurate. And that most people shooting an A7R are going to be using adapters so there were some real-world reasons for looking at them. I countered that we'd have to test a number of adapters with each lens to find the most accurate one and that would take hours. He replied that we had some wide-angle lenses that needed optical adjustment and that's what we'd be doing if we weren't testing. Game, set, and match to Aaron. There's nothing I hate more than optical adjustments on wide-angle lenses.

To make things as accurate as possible, we tested a number of copies of each lens on a number of copies of brand-name adapters and took the best combination to present below. Again, let me emphasize that adapters that are perfectly fine for taking pictures (all of the ones we tried) aren't usually fine for generating testing numbers. A bit of field tilt, for example, makes no difference in a 3-dimensional picture. (If the grass on the left side is in best focus a foot further away than the grass on the right side, it really makes no difference. If the focus on the test chart is a two inches different between the right side and the left side, the numbers on one side are awful.)

So what I'm showing you is the best lens-adapter-camera combinations we could find - but please realize that especially off-axis, the numbers we get from adapters are more variable than what we would see from a camera with native lenses mounted.

(As an aside, people always ask 'what adapter brand is best'. It's not a brand. We use mostly Voigtlander, Metabones, and MTF adapters, which we think have good quality overall. But with 4 interfaces -- one lens, 2 adapter, one camera -- there is inevitable variation. Adapters are like sausage. If you love sausage, you definitely do not want to know too much about how it is made. Same with adapters. The quality control isn't what you hope it is.)

Canon 35mm f/2 IS

Since we had tested the Sony-Zeiss 35mm we thought we'd try a couple of other 35mm lenses. We started with the Canon 35mm f/2 IS lens - since we have extensive data testing this lens on Canon 5D II cameras we thought it would be interesting to see how it fared on a higher resolution sensor. We tried a few copies of the Metabones Mk III EF to NEX adapter and used the results from the best lens-adapter combination. The table below compares the results with this lens on an A7R and a 5D II.

Ctr MTF50 Avg MTF50 Avg Corner MTF50
5DII2@f/2840715400
5DII@f/41045870570
A7R@f/21050875385
A7R@f/414001160560

Obviously the A7R brings out some dramatic capabilities in the center of the 35mm f/2 IS lens that the 5D Mk II can't show us. But the amazing performance doesn't seem to carry out to the corners.

I think it's important to look at what's going on in the corners, so I'm going to go a bit geeky on you for a minute and show you actual Imatest printouts for the 35mmf/2 IS on the A7R. Below are the printouts at f/2 followed by f/4.

 

 

The top image, at f/2, demonstrates the little bit of tilt that is still present with our best lens-adapter match. The lower left corner is quite good, the upper right rather weak, and the other two corners in-between. This would be barely noticeable in a picture. But it makes the corner resolution numbers in testing quite questionable. Especially when you only see the average number like the table above.

In the second image, shot at f/4, the increased depth of  field seems to make up for the tilt affecting the corners. But if you look carefully there is still a significant difference in the numbers for vertical and horizontal resolutions, particularly in the middle third of the lens. Astigmatism in the lens could cause something like this, too, but this is a lens we know doesn't have much astigmatism.

So we can take away that the resolution in the center of the Canon lens adapted to the A7R is awesome. The corners are very good, but not spectacular. Why the difference between center and corners? Could be adapter. Could be sensor microsensors. Could be chromatic aberration. Could be something done during in-camera processing of raw images (these are raw shots, so no jpg conversion is taking place). In other words, I don't know. But as with all unexpected results, we repeated the test and it was consistent.

Zeiss ZE 35mm f/2

As long as we were shooting at 35mm we thought we'd try the Zeiss 35mm f/2 on the A7R. Even wide open at f/2 the numbers were pretty spectacular. Again, in the table below we'll compare the ZE 35mm f/2 on the Canon 5DII and the Sony A7R.

MTF50 Ctr MTF50 Avg MTF50 Avg Corner
5D Mk II875770570
A7R12351025600

The same pattern shows again; dramatic improvement in MTF50 in the center with the A7R compared to what we would see on a 5D II, but only a slight improvement in the corners. In this set the adapter gave us quite even corners, although, again, we did have some astigmatism off-axis that pulled the numbers down a bit.

At this point I did wonder if my choice of 35mm lenses might be part of the corner issues we were seeing. There are plenty of reports that wide-angle lenses have problems in the corners on cameras with short flange-to-sensor distances like the A7R. So I did want to try at least one set of longer lenses to see if the pattern continued.

A Set of 50mm Lenses

I chose a couple of 50mm lenses for the next test, mostly because I wanted to try at least one Leica lens. (Wide angle Leica lenses on the A7R are another topic entirely, and too big of a topic for me.) We had a Leica 50mm f/2 APO-SummicronASPH handy, and thought the Zeiss ZE 50mm f/2 Makro Planar would make a nice comparison. We used a Voigtlander M to NEX adapter for the Leica and another Metabones Mk III for the ZE. (For both I'm using the best results of 4 adapters tried.)

MTF50 Ctr MTF50 Avg MTF50 Avg Corner
Leica @ f/2 A7R13651205680
Leica @ f/2.8 A7R15501200710
Zeiss @ f/21335910410
Zeiss @ f/2.81410960440
Leica @f/2 M2401075970725
Leica @f/2.8 M24011351015840

The most interesting comparison, here, I think is the Leica 50mm lens on the A7R and on its native Leica 240 camera. In the center, the A7R has much higher resolution than the Leica 240; it's 36 megapixels versus 24, after all. But the corner numbers are more interesting. Here the Leica camera has resolution slightly higher than the A7R.

Given that the 50mm is not a retrofocus design, there shouldn't be major corner issues with the A7R. Of course, there's no way to rule out an effect from the adapter, although this was the best result with 4 adapters (all on the same lens, though, we only had one copy in stock).

Leica has said a lot about how their camera's microlenses are angled in the edges and corners, maximizing the sensor's performance with their own lenses. This is a very isolated finding of one lens on one camera, but it does seem to support that.

Conclusion

I'm not anti-adapter, by any means, and I wouldn't hesitate to shoot a good lens on an adapter with the A7R. It's important to bear in mind that numerical testing differences don't always equate to significant picture differences. But there do seem to be some limitations.

If I were to make a quick summary:

  • The A7R delivers amazing resolution. At least as good as a Nikon D800e.
  • The two Sony-Zeiss prime lenses (the 35mm we tested, and the 55mm tested by SLRgear.com) are excellent. Hopefully other native-mount lenses will also be excellent.
  • Other-brand, standard-range (35mm and up) shot on a well-matched adapter give superb center resolution, better than you would get on the native mount camera, unless that camera is a D800e. Corner resolution is very good, although less than amazing.
  • Given past experience, and several early reports, shooting lenses wider than 35mm on an adapter is going to be a bit more challenging. I doubt we'll be able to make too many generalizations. Rather each lens will have to be evaluated on the A7R to see how it performs.

My own conclusion is pretty simple: I need to spend some time investigating the A7R and it's lenses. This is a small test group of lenses, but every single one resolved better in the center on the A7R than it did on any other camera. This is going to be attractive to a lot of people who have been lusting for a high resolution sensor but didn't have one available in their lens mount.

There are plenty of questions remaining, of course. The corner numbers may be just an artifact of testing on a flat, two-dimensional field. In real 3-dimensional photography things might be much better. This alone is going to require a lot of information by numerous testers before we get a good handle on it. It may go away when we get to slightly longer focal lengths. It may be something seen in only a few lenses and we just happened to pick those to test.

Even if the laboratory corner numbers reflect photography reality, though, remember the corners on the A7R are (except for the Leica lens) at least as good, if not somewhat better than the native camera mount. So the rising tide of the A7R sensor lifts all the boats in the center for sure. I'm still not certain about the corners.

So while I'm not ready to jump on the "this camera is going to change everything" bandwagon just yet, it certainly has the potential to change some things. Assuming some good third-party lenses become available in FE mount soon, and Sony continues to broaden the lens lineup with excellent glass instead of 10X variable aperture superzooms, it may change a whole lot of things.

 

Roger Cicala and Aaron Closz

Lensrentals.com

December, 2013

47 Responses to “Sony A7R: A Rising Tide Lifts All the Boats?”

Chris said:

I wonder if the D800E resolution suffers a bit compared to the A7R because of the AA "canceling" filter assembly as compared to no AA filter. The difference between the D800 with and without E is rather small.

Kerry said:

Thanks for another fascinating blog post! Do the less than spectacular results in the corners possibly mean that the glass filter covering the Sony A7r sensor is too thick and is smearing the angled rays? Might this be tested by tilting a lens and looking for sharper performance as the corner ray angle is decreased? ... Or testing by removing the sensor filter, and seeing if the corners get much sharper.

LensRentals Employee

Roger Cicala said:

Chris and Kerry - I think you've both got excellent points and they make perfect sense. Kerry, Fred Miranda has been working with a 17 TS-E lens on several adapters and seems to be seeing worsening of the corners with increased tilt.

Roger

Ingo said:

Damn, every single review of the A7/A7r and the FE-35f28 and FE5518 it's getting harder and harder to resist...
Now, we have Roger and Lensrentals, whom I respect the most and he is quite "optimistic"...
Goddamn, I have to earn more money...

gary said:

Can you test the zeiss otus 55mm on the a7r? I think it would post some fairly impressive figures for central sharpness.

Since the e-mount lenses are designed a much with shorter registry distance, the angle the light hits the sensor is different on an e-mount lens to an adapted non e-mount, if Sony has optimised the sensor (I can remember a rumour about some macro-lens on sensor optimisation to improve corner sharpness), could this explain the drop in corner sharpness on the non e mount lenses? The central sharpness shouldn't be affected as much by this because the light will be travelling at a closer angle to the e-mount lenses.

LensRentals Employee

Roger Cicala said:

Gary, I would if we could keep one in stock long enough to try. I'm like you, I think it would be absolutely spectacular.

Samuel H said:

Thanks a lot for all these tests, but man, you're killing me: now my vintage Leica-R lenses want to live on an A7r instead of their current NEX+SpeedBooster...

Gary Morris said:

I've been shooting the A7R with the current Leica 50mm Summicron (non-APO) (via the Voigtlander adapter). From f5.6 to f11 the sharpness appears to be crazy insane sharp across the image. Much better than on my M9. Again, just one lens on one body but very convincing. I also tried out my 50mm Summilux and it too is very sharp (I just don't like using this lens so I took far fewer pictures). Finally, I shot a number of pictures with the Voigtlander 35mm f1.2 II. Again, very sharp and no color shifts at higher f-stops. But… wide open the CA was very noticeable. More so than using the Leica glass. Parenthetically, the Voigtlander lens is superb on my NEX6. After the holidays I'll do some serious shooting with the A7R, Voigtlander adapter and my Noctilux f.95. Should be fun!

Erik Magnuson said:

IIRC, no AA-filter is like sharpening for it's impact on Imatest MTF50 calculations which makes comparison of systems with/without AA filters problematic.

James Scholz said:

Thanks again, Roger, for your very interesting article. You may have addressed it in the past, but I have a question about how much difference in the numbers is required to see a difference in a 20x30 inch print, my usual print size from my D800e. Would one notice a difference between 1000 and 1100 for instance, or would the gap need to be wider?

LensRentals Employee

Roger Cicala said:

James,
It's not a direct correlation, but a difference that is at least 100 line pairs and 10% different should be visible in that kind of print. So the difference between 1000 and 1100 would be right at that point.

William Jaeger said:

I'm wondering here (as elsewhere) if the corner numbers fall off because the plane of focus shifts front or back from the center focus. What that would mean is, it might be very very sharp a little closer or farther from the camera, which means further that the corner tests only really matter in doing flat copy work.

Which most of us never (or rarely) do.

To test--could the corner tests be done with the lens re-focussed for maximum corner sharpness?? (I'm assuming this is NOT the case as is.)

Put another way, if Robert Frank or James Nachtwey are in the field shooting with a great lens, wouldn't the corners be sharper than you imply, since the actual focus points are all over the place?

Great great article as usual.
Bill

LensRentals Employee

Roger Cicala said:

Bill, sort of. We did focus before and past the center focus point to see if it was a simple field curvature and while there is a little bit, like most lenses, it doesn't bring the corners up to a point you'd expect given the center numbers.

jubi said:

thanks for all your work.
Some say that is not about the camera, is about the person behind. But here was no camera that improved my style and my understanding of photography as did a NEX with a manual lens (on that bloody adapter, with that little tilting screen). Now I am stuck with Nikon, (and very pleased about the system) but, damn, the little a7r is a lot of a camera.

Matt said:

Couldn't the corner performance on the fe 35 be so much better because there are in camera corrections being made like the Leica M does with Leica lenses. If that's the case then waiting for the lens line up to become more mature will be easier. Also, are you planning on checking out the difference between the 7 and 7r with the fe 35 and did you notice the reported shutter vibration on the 7r?

Max said:

I have been Imatesting the camera and it's great (in B&W) but if you look through these photos you will see that the cameras compression doesn't translate to great photos in color unless using a wide angle and shooting a detailed composition. File sizes also show this.

There is a problem with Sony compression in RAW and it has considerable and secondary effects when compressing to JPEG with or without post.

http://www.flickr.com/photos/110671606@N08/

Matthew Youngberg said:

Would the better corner performance on the fe 35 be from in camera fixes? Also did you notice the reported shutter vibration with the 7r? Last one, were you going to check the numbers on the A7 as well, I'm still debating between the two as the 35 is basically free with the A7 and combined it's cheaper than the RX1.

Max said:

I have been Imatesting the camera and it's great (in B&W) but if you look through these photos you will see that the cameras compression doesn't translate to great photos in color unless using a wide angle and shooting a detailed composition. File sizes also show this.

There is a problem with Sony compression in RAW and it has considerable and secondary effects when compressing to JPEG with or without post.

CarVac said:

@Max:

That doesn't make much sense. What sort of compression?

Usually, lossy compression would hurt the wideangle, high-detail scenes you mention more, not less, than it hurts shallow-DOF telephoto shots.

Max said:

The Nikon guys have no problem seeing it.

http://www.fredmiranda.com/forum/topic/1260660

The A7r all are about 37mb out of the camera. My understanding is that D800 files can be as large as 76mp.

One analysis shows that Sony does the following in their compression

http://tinyurl.com/kuhakb8

0-800 contains 801 unique values ​​(ie is continuous)
801-1424 contains 320 unique values ​​(skips 1 out of every 2)
1424-1427 contains one unique value (skips 2 of 3)
1428-2023 contains 149 unique values ​​(skips 3 of 4)
2024-2029 contains one unique value (skips 5 of 6)
2030-4093 contains 258 unique values ​​(skips of 8)

Digilloyd also discusses the issue

Max said:

CarVac - I just noticed that I didn't answer your question 100% - here's the file sizes after LR5.3 http://flic.kr/p/ioohLj (same basic scene - the photos also in that flickr page)

CarVac said:

Max, I must apologize. When I wrote that post I only saw the second copy of your post which didn't have your URL.

Now I see it: strange color artifacts in gradients that shouldn't occur normally, which are imperceptible in regions of high detail.

Richard said:

Could you try testing the Sigma 35mm F1.4 Art on the A7r/D800e against the Sony Zeiss 35 2.8. Interesting to see how well the Sigma performs on the A7R given it is one of the best 35mm lenses for DSLRs.

derek said:

First Thanks Roger.
I have all gear used for this test here, and I also got the 55mm f1.8 ZA SSM, it is safe to say the 55mm is even sharper than this 35mm f2.8.

I think the Sony 55mm f1.8 may actually rival the Otus.

Seriously in terms of pure resolution , the Sony A7R is a game changer.

But IMO, the pro of it ends just right there(there is nothing good about it other than the sensor), it is as a system camera not practical(unless you already have a lot of digital Leica M primes).

I think most of SLR lenses are too heavy to be useless on this body due to the weak fragile mount design(it should have been a bit bigger).

I mounted my Leica 180mm f2.8 R lens , Zeiss 50mm f2 MP and Nikon AF-S105mmf2.8GVR Micro Nikkor via adapters,it seems like the weight of the heavy D-SLR or SLR lens really put too much stress on the WEAK mount, and just after a month of light use with my Leica R and Zeiss ZF primes , my poor A7R 's metal mount is already wobbling and I will have to ask Sony to tighten it up again(this is my second time to ask this).

The AF of the 7R is the worst of all types AFs I have ever tried in real life, it misses anything even slowly moving(shooting flowers in a windy day is extremely difficult with this camera).

It hunts hunts hunts in a bit dim light, in fact it focuses a bit better with the 24mmf1.8 ZA than any other E mount prime(I have almost all E mount lenses), but it is still too slow to be usable in lowlight.
The EVF is better than my NEX7 but a bit worse than that of the EM1 or the XE2.
So in the end , as much as I like the idea behind this camera , I do not find it any practical and I will not sell it soon.

I will try the normal A7 since I do not want to lose too much money by selling all my Sony E mount lenses , but I am not too optimistic about it either.

John said:

Roger:
Thanks for the interesting report. I just rented the A7 and a 35mm f2.8 last week from you folks and found both to be excellent pieces of kit. Since I didn't also rent the A7R I was wondering if you might have had a chance to compare the low light autofocus capabilities of the two cameras comparatively? I've heard stories of one being better than the other both ways and I wanted to find out which was true before purchasing either.

Regards,
John

anurag agnihotri said:

Hi Roger,
Looks like this Sony is scared of tele lenses and starts chattering its teeth whenever it meets one. Will you be interested in a diagnosis?
Not related to this, but i hope a surgical procedure on the body is in order at some point in time, considering you are an expert surgeon.

Joachim / CH said:

It's really interesting how some guys generously spend other people's time :D

Thanks for this article, Roger. I also spend some time now on Sony's website, but after that I'm not much more aware of a variety of Sony/Zeiss lenses than I was before. Is it because they have to share the webspace with all those fancy TVs, Hifis, playstations and whatever they jam into radio market's corners? Or are there really only 5 E-lenses?

LensRentals Employee

Roger Cicala said:

That sounds about right Jachim. And after they've released the 35mm and 55mm FE lenses, that makes a total of, uhm, 2 good lenses :-)

Joachim / CH said:

Right, and those seem to be very promising. Sony had lots of those good starts but as long as they treat their cameras as another walkman it's really challenging to take them serious. Somehow they don't get the difference between consuming content and producing it?

Jonathan Slack said:

Fascinating article as always Roger.
With respect to angled micro lenses - the M9 definitely had them, but I think the M(240) doesn't - CMOSIS made a thinner top layer of the sensor to allow the angled light to enter (which in turn improved the situation with colour shifts).

I'm wondering whether the poorer edge definition may actually be a function of the Sony angled micro lenses?

Derek said:
*"But IMO, the pro of it ends just right there(there is nothing good about it other than the sensor), it is as a system camera not practical(unless you already have a lot of digital Leica M primes)."*

I thought this as well, and that's why I bought the camera - but I found that (with some exceptions like the WATE) it was really not so good with anything wider than 50mm (corner smearing). So I took it back again.

I reckon that it all boils down to whether the native lenses are all good (the 24-70 f4 zoom for instance).

NormSchulttze said:

The Sony A7r is said by a few internet commentaters to suffer from significant shutter bounce. Causing image deterioration. How say you ?

LensRentals Employee

Roger Cicala said:

Jonathan, after a number of conversations with people smarter than me and the consensus is it's probably not microlenses - it's the thickness of the cover glass. That's causing refraction in lenses with exit pupils near the rear of the lens, which includes all of the wider angle Leica lenses I believe.

LensRentals Employee

Roger Cicala said:

Norman, I don't have a comment: not something we have really looked at, too subjective for me.

marc aurel said:

Dear Roger,

thanks for your work on this. I love your extremely useful examinations of technical problems.
There could be another reason for the bad corner performance with canon lenses on the A7R: internal reflections in the metabones-adapter. With a TS-E and full shift there is a degradgation of contrast in the shifted area of the A7R image compared to the 5DIII - the A7r image looks worse than the canon. This has been reported on various forums be different people.
So I bought some self-adhesive velour to cover the interior of the metabones - Canon uses something similar for the interior of the TS-Es. I repeated the test. Now the A7R was much better. I wrote a topic about it on luminous landscape (Forum Cameras, Lenses and shooting gear). There are samples of before and after and instructions how it can be done:
http://www.luminous-landscape.com/forum/index.php?topic=85249.0

I suspect that the degradation because of reflections in the adpater is not restricted to the extreme corners. So this could be part of the reason for the bad numbers you get for the corners of other canon lenses.

LensRentals Employee

Roger Cicala said:

Hi Marc,

I saw that. I'm going to give it a try with some flat paint. I think even then the cover glass refraction is going to have a lot of contribution off-axis.

Great point, though,and I bet it does contribute.

LensRentals Employee

Roger Cicala said:

Hi Roger,

thanks.
I’m not sure, but I think that reflections are better absobed by fabric than by an even surface of paint – no matter how matt. The black fibres in the velour spread the light that they can’t absorb in all directions. Parts of it hit other fibres and are absorbed too. Canon does the same inside their TS-Es. But it would be interesting to compare both solutions. An advantage of the cloth is its reversability (on 400,-€ adapter this is an advantage).

The good thing is that the possible image quality is even better than I thought in the beginning. Altough i would still prefer a canon dslr with a sensor like the one in the sony. I prefer the size and weight and handling and the optical viewfinder.

With best regards – marc aurel

LensRentals Employee

Roger Cicala said:

Marc, from what I've heard it seems to really help the tilt=shifts, which make sense. I was hoping it would help corner resolution with standard lenses, but in my tests, at least, it didn't seem to.

Samuel H said:

Makes sense: a tilt-shift lens can through a pretty big chunk of the light cone into the sides of the adapter, but that is unlikely to happen with regular lenses.

Samuel H said:

Also: if it's the cover glass, I would expect a revised A7r+ version soon, much like the Nikon D610. Thankfully, because it's a reason to wait and my wallet was really burning in my pocket...

Scott Kirkpatrick said:

How can you be sure that Sony in the A7 isn't sharpening the raw files? They also compress lossily, I gather, so they are not committed to having a raw file that is really raw, just the count of photons per pixel. One test might be to look not just at the MTF 50 numbers, but at the MTF curves as a function of spatial frequency from 0 to Nyquist. If there is some sharpening going on, the curve won't simply drop steadily but can curve up at first before falling off. I've used this test to tell if "zero sharpening" in raw file development software is really zero. Usually it is not.

LensRentals Employee

Roger Cicala said:

Scott, I agree, and I'm certain they are playing with raw files. But I'm left with 'whatever it is is what it is'. Not much I can do about it.

Tom Cavanaugh (TCav) said:

Thanks for another excellent, thought provoking article.

Your testing of a Canon 35mm f/2 IS on a Sony A7R provoked a thought of my own. Do any adapters provide the power necessary for the in-lens image stabilization to function?

Oskar Ojala said:

Thanks for the post -- all the analysis of the new Sonys is needed!

I'm leaning towards the cover glass too; it has caused me many challenges with APS-C Nex cameras. I'm also thinking about the ill effects that an interference IRUV filter can cause when rays do not arrive perpendicularly. But it's still disconcerting that problems arise even with such relatively long focal lengths as tested here; the A7r is not very appealing if the shortest usable lens is 35 mm, one needs to buy all new lenses and only workable wides are huge designs for traditional SLRs.

I don't have any calculations for how much mount tilt could affect maximal achievable resolution, nor do I know how much tilt there can be without anything being broken. Any insights on those?

Jim Olsen said:

This is great information, thank you for the effort. I know how hard it can be to get sufficient test data to draw appropriate conclusions. This is a great start. I have been testing my A7R with a bunch of Canon FD and M42 Pentax lenses. I am seeing a noticeable difference in corner sharpness depending on if I focus in center or at corner, even at f/11. It doesn't appear that stopping down changes this, regardless of the apparent increase in DOF. Did you try focusing at the corners to see if resolution changed significantly? I have found that when photographing landscapes, I can determine focus point for both center and corner and then split the difference or bias one way or the other depending on preference.

Jim Olsen said:

Roger,

I found the article written by you and Tim Ashley discussing field curvature and how to deal with it. I ran more tests on my FD wides with A7R and I don't think the curvature is too extreme. Now that I know it exists and in which direction for both my 20/2.8 and 24/2.0 I can make adjustments when needed for specific shots. When I adjust focus, both lenses are much sharper in corners at f/8 than I originally thought.

Anton said:

What is the sense of comparing two systems, if you have said before, that A7r's raw-files are cooked?
What will happen if you apply smart sharpening to Nikon or Canon file?
On photozone.de they say, that a simple sharpening can improve those numbers by 30% easily, if not more.

Andy said:

More resolution increase in the centre than at the edges when comparing 24 vs 36MP? Sounds familiar - just like the Sigma35 1.4 on a 5D2 and D800 (DxO lens data comparison widget at DPR : http://www.dpreview.com/reviews/lens-widget-fullscreen?compare=true&lensId=sigma_35_1p4&cameraId=canon_eos5dmkii&version=0&fl=35&av=4&view=mtf-ca&lensId2=sigma_35_1p4&cameraId2=nikon_d800&version2=0&fl2=35&av2=4 )
5d2 centre ~2300 Edge ~1700
D800 centre ~2950 Edge ~1700
Of course, the Sigma mounts for Nikon and Canon might be regarded as "Sigma adapters" :D
They also tested the same lens on 7D and D700 and found increasing centre resolution (when re-normalized to LW/mm) as pixel size shrank, but the proportional increase was smaller with each increase in pixel density. The lower MTF 50 at the edge of the lens contributes a greater and greater amoun to the overall result as the sensors are able to record the deficiencies more and more accurately. We see the increased resolution in the centre because previous data were severely limited by the sensor's MTF curve. With the Sigma 120-300 at 200mm at f/4 the edge performance of D800 and 5D3 was the same at ~1600, but the centre enhancement was trivial ~2650 vs ~2500 respectively. One would expect the MTF fall-off at the edges is smaller for tele vs wideangle. The product (convolution?) of lens MTF and sensor MTF gets very complicated as a function of lens design (here I mean MTF50 across the lens as your plots dsplay, not the MTF value for 30lp/mm in their calculated charts) and sensor angle, AA filter, microlens offset (although that might affect vignetting more than resolution but the angle thing alters the incoming Lp/mm at the edges of a wide-angle more than for a tele etc etc etc....
Finally: bottom line is - it's not necessarily the adapter.

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