The Sony A7r: Dealing with an Existential Camera Crisis

Sony A7r + Canon 24mm TS-EII (2 images stitched)

With all of the recent sound and fury on camera forums pertaining to the Sony A7r, and after many weeks of scrutinizing online samples, reading wildly varying opinions, and finally taking on extensive testing with an A7r of my own (both with native lenses and in combination with several different adapters) I found myself lost in an existential camera crisis. What is the true value of this camera? What purpose does it serve? Is it worth it?

Everyone of course will have their own opinions on how to answer such questions. But to borrow a phrase from Søren Kierkegaard, “I must find a truth that is true for me.”

With that, I decided to focus first on what occupies a large portion of my shooting: Canon’s TS-E lenses. When the Sony A7r was announced, there was quite a stir among those of us who use the marvelous TS-E optics (specifically the 17mm TS-E and 24mm TS-E II.) These are the two lenses that all these years have kept me tethered to the Canon system. Nikon’s D800 camera had a wondrous Sony sensor with more resolution and amazing dynamic range, but it wasn’t enough to convince me to give up my TS-Es. So I stuck with my trusty 5DII, certainly a capable camera, and decided to wait for the day that Canon would inevitably catch up in the sensor department.

But then came the A7r, and suddenly I was presented with the possibility to match my TS-E lenses to a Sony 36mp sensor—albeit with an adapter between them. The downside is that by adding more lens-to-camera interfaces, you increase the likelihood of misalignments of the lens to the sensor plane. As Roger Cicala brought to the attention of many photographers, There is no Free Lunch. (Or, as I was thinking as I was shooting the photo at the top of this post, There is no Free Parking.) The question is how noticeable will those misalignments be in real world photos?

I had that nagging concern, but still, the temptation was too great. (And perhaps just as crucially to my purchasing decision, it had been far too long since I had bought a shiny new piece of technology.) So armed with an A7r and a Metabones adapter, I decided to transpose my existential questions into practical questions. If I mount a TS-E lens to my A7r, will I get better results? Are there any circumstances I will ever get a worse result?

What I did was shoot scenes with my 5DII and A7r, and compare the results by upscaling the 5DII files (to see where the A7r files are better) as well as by downscaling the A7r to the 5DII files (to check if the A7r files were ever worse). Yes, I know some people will say “It’s not fair to the 5DII to interpolate the images.” But that’s the whole point in my view of comparing it to a camera with more resolution. It’s not supposed to be a level playing field. In theory, the higher megapixel sensor is supposed to deliver better results than the camera you have to upscale. I wanted to know if using the adapter would wipe out the benefit of the extra resolution.

After a number of tests I’ve come to the following conclusions:

  • There is indeed a discernible gain in resolution when using the A7r. It may not be huge, but it is noticeable, especially in the center.
  • The resolution gain is still apparent even when the lenses are shifted.
  • The difference in resolution starts to diminish as the aperture gets stopped down and diffraction creeps in, but more resolution is still noticeable in my opinion at least up to f/13.
  • The corners will get soft on the A7r, but they do not seem to ever get worse than the 5DII, even when shifted (and in a couple of circumstances even stayed very slightly better). The discrepancy between sharp center to soft corner is more noticeable on an A7r (and more so at wider apertures)…but of course if this affects “real world” photos depends on the level of detail in the corners.
  • When the A7r files are downsampled to 5DII size, in some circumstances the resolution benefit can still be noticed.
  • The A7r with the adapter is vulnerable to strange flare effects, likely due to internal reflections. (Masking the inside of the adapter can solve this issue but I haven’t had a chance to try this myself yet.)

Now comes the point where I present a few of the examples. First, we start with the 17mm TS-E unshifted, stopped down to f/13. I was interested if there would still be any resolution benefit after diffraction took its toll. The 5DII holds up pretty well, but the A7r does indeed show a little better. Full scene and crops follow below (click on the crops for 100% magnification).

17mm TS-E, f/13, unshifted, full scene

17mm TS-E comparison, unshifted, center

17mm comparison, unshifted, corner

Now here are the results at maximum shift (I shifted to the side instead of shifting up, since shifting up would have produced only empty sky with no detail for comparison). Center areas of the image are still showing better resolution on the A7r. Top left corner seems about the same; bottom left seems a little bit better with the A7r.

17mm shift left, full scene

17mm comparison, max shift, near center

17mm comparison, max shift, top corner

17mm comparison, max shift, bottom corner

17mm comparison, bottom corner, A7r downscaled to 5DII size

Now, here is a set with the 24mm TS-E, shot at f/8. At this aperture, the advantage of the A7r seems a little more pronounced.

24mm TS-EII, unshifted, full view

24mm TS-EII comparison, unshifted, near center

24mm TS-EII comparison, unshifted, upper right corner

24mm TS-EII comparison, unshifted, lower left corner

In this scene, I did see some softness appear at the extreme edges of the frame, though again in absolute terms it doesn’t seem worse than the 5DII. This particular example shows how the A7r can go from noticeably more resolution to about the same as the 5DII, apparent in both 5DII upscaled and A7r downscaled scenarios:

24mm TS-EII comparison, towards edge of frame

24mm TS-EII comparison, towards edge of frame, downscaled

As seen before in the 17mm samples, upper corners on the A7r become soft to the point it’s about the same resolution as the 5DII…the center of the frame stays sharper (for brevity only the downscaled to 5DII sized images are posted here):

24m TS-E II comparison, full shift, near center, downscaled to 5DII size

24mm TS-EII comparison, upper right corner, downscaled to 5DII size

So, have I resolved my existential camera crisis?

The resolution question for adapted lenses, I think I’ve at least put to rest in my own mind. Yes, the corners get soft with the wide angle TS-Es, but not soft enough to discourage me from using the camera. Yes, the relative softness to sharpness discrepancy is more than what I’d see using my native Canon body. But, the native body is also going to have less overall resolution, and its corners are going to be soft as well. If I were to go through my portfolio at 100% zoom on a computer screen, most of my photos would not look critically sharp in the corners, and this hasn’t bothered me before. So I don’t think this is really going to ruin any A7r images. The only real downside that irks me is the flare issue…but knowing that there is a relatively easy fix for that, I’m merely annoyed instead of stressed out by it.

And overall, I just have to comment that I really like using the A7r and working with its files. I don’t want to get into lengthy discussions on dynamic range or post processing at this point, since I just want to spend some more time working with more files in a greater range of scenarios … but I will say that my initial impressions are positive. In terms of overall image quality, I’m happy so far.

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Oakland, Oct 2013

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San Francisco.

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Time and Space

From the theory relativity, we know that time and space are both part of the same thing. Yet we can’t help but perceive them as separate. And we are always measuring and dividing them down into small units.

Maybe it’s because that way we can trick ourselves into not feeling small.

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Union Square, San Francisco.

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Reno, NV.

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Dream in Concrete

Yerba Buena Gardens, San Francisco.

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Perspective Correction: Lens vs. Software

I’ve been coming across a lot of discussion of tilt-shift lenses recently. One of the particular benefits of these lenses is the ability to apply perspective correction to a scene by shifting the lens up or down. This allows the photographer to keep the camera level, which means that vertical lines stay straight instead of leaning backward (if you’re pointing the camera up toward the sky) or forward (if you’re pointing the camera towards the ground).

I use the shift function extensively in architecture photography, where it’s especially important to keep lines straight. But, shift can be useful elsewhere too. In landscape photography, for instance, a photograph generally works better if the horizon is not in the center of the frame. But, if you compose with the camera level, that’s just where the horizon will be. To move the horizon off center, you can point your camera up or down. That may not big a big deal. But, let’s say you have some nice tall trees in the picture. Those trees will end up looking like they’re leaning. And, the wider the focal length, the more problematic this can be.

One way to solve this is to use a T/S lens to shift the composition. Another way is to use perspective correction in software after the fact. Now, some people will tell you that correcting perspective in software can cause a degradation in image quality because you’re pushing pixels around in your image. Technically that’s true. But, unless the corrections are extreme, the degradation is pretty small. Honestly, I wouldn’t be too worried about that unless you’re making large prints. However, you do need to be concerned about cropping away a lot of your composition.

Here’s an example. These images were shot with a Canon 17mm TS-E lens. The top image is unshifted, with the camera tilted up to capture the entire tree in the frame. The bottom image is with the camera level and the lens shifted up about 6mm. (Keep in mind that 6mm is what I’d consider to be a moderate amount of shift…full shift is 12mm.)

Now, let’s look at what happens to the unshifted image when we apply perspective correction in software to try and match the shifted image. The software has to progressively stretch the image out towards the top, while pulling it up at the bottom:

So once you’ve done this, you have to crop the image:

We can correct the perspective to make it look a lot like the shifted version, but we end up having to cut out a significant portion of the composition. In the unshifted version after correction, the composition ends up off balance with the tree now too close to the edge of the frame. Overall, in the corrected version, you end up throwing away about 20% of your original pixels.

As far as what the pixels look like themselves, let’s have a look at that slight degradation in image quality.

Unshifted, corrected in software:


So yes, correcting for perspective in software does cause a bit of degradation, but I don’t think it’s extreme and probably won’t be noticeable unless you’re making larger prints.

But again, remember that the above example is only a 6mm shift. The more perspective correction that’s required, the more problems you’ll run into trying to do that correction in software, in some cases running your subject completely out of the frame. As an example, consider this image:

This image was also shot with a Canon 17mm TS-E, but at full shift. It would’ve been very difficult to try and replicate this composition with a non-shift lens and maintain the entire building in the frame (needing to resort to an even wider focal length, or stitching of multiple images).

So, in summary: yes, software correction can be a very useful tool to correct perspective if you’re not working with a shift lens. But, if you intend to use it, you need to be very careful when you’re shooting and plan ahead by incorporating extra space into your composition which will need to get cropped away.

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San Francisco, CA.

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