I'm not sure where print came into play. I think, when evaluating sharpness, the only thing that really matters is actual image dimensions. The 7D's physical APS-C frame is indeed smaller than the 5D III's by the ratio you mention, but the output image is MUCH closer to the 5D III's output image dimensions.
The 5D III full RAW image size is 5760x3840. The 7D full RAW image size is 5184x3456. In relative terms, the image sizes are red and blue below, where as your skewed sizing, based on physical sensor dimensions, greatly puts the 7D at an undue and unrealistic disadvantage (green):
I know you dislike the 7D, but I think you are making a very unfair comparison that isn't benefiting the underlying point at all. The 7D it IS capable of being razor sharp, even with the 100-400...and with that particular lens, the 7D is not capable of really reaching its full potential.
I don't think chasinglight's problem is that he is using a 7D. Far more likely than that, I think there is probably some lens/body tuning that could be done, and after that, it is largely a matter of technique. If you use a tool properly, you can maximize it's potential, and the 7D has a LOT of potential. That doesn't mean it will produce better results if you have the ability to fill the frame with both the 7D and the 5D III...the simple fact that the 5D III has more total pixels means it will produce a better image. All it means is that chasinglight can work on a few things that cost him nothing, yet allow him to produce better results.
I don't quite know where to start addressing this post.
I think the best thing would be for you to go and reread the thread.
I'm not debating the entire thread...only "Reply #38", where I believe you to make an incorrect comparison between a 7D image and a 5D III image by scaling the 7D incorrectly, which results in a significant and further reduction in detail of the 7D image relative to the 5D III image. When it comes to what was actually resolved, magnification relative to the final output is not the sole factor.
I am the one who has constantly said the 7D is a more than capable camera, how you have managed to infer from that "I know you dislike the 7D" , I just don't fathom and am in complete disbelief at.
You've come off at me fairly strong in a number of threads over the last couple of months where you seem to put the 7D in exceptionally bad light relative to other cameras. You have repeatedly made a point of calling out how the 7D's resolution advantage is effectively meaningless. Given the repetition, I can only conclude you dislike the 7D. I also still believe you are comparing things incorrectly, and putting the 7D in unfair light. Even detailed articles about the 7D's resolution advantage from a well respected Ph.D., Roger Clark, seem insufficient to get you to even meet at some middle ground.
Sorry if I've misread you, but I've been going by both the intensity of your responses to me when I debate the issue with you, and the frequency at which you bring up how nearly worthless the 7D's resolution advantage supposedly is.
Further "The 7D it IS capable of being razor sharp, even with the 100-400.." I KNOW, and I posted 11 links of razor sharp images shot with a 7D and 100-400, of birds, at 400, and some wide open!!!!! DID YOU NOT SEE THEM?
No, I came in on page three, I guess...saw a post by you that put the 7D in unfairly poor light, and responded. Again, I wasn't responding to the entire thread, and having read through the rest, I'm a bit confused by what seems to be conflicting information in different posts.
Or this "I don't think chasinglight's problem is that he is using a 7D" I have repeatedly said his main problem is subject distance (magnification) NOT THE 7D. Funnily enough that is why I used MAGNIFICATION as the comparison between his and Alan's images.
Using magnification alone, and ignoring pixel sizes completely, is the issue I was debating. I think that is oversimplifying the issue. There are effectively an unlimited number of potential output sizes, both smaller and larger than the native image size for each camera. I think it is only fair to compare them at their native sizes. Assuming the same bird is photographed at the same distance with both cameras, there is both a magnification difference as well as a pixels on subject difference. Since the issue is sharpness, pixels on subject matter. This is effectively a pixel peeping situation, so considerably reducing the size of the 7D's native output is skewing the basis for comparison.
I get the feeling we are just going to agree to disagree on this point...so I'm happy to end the debate here.
Alan suggested an $8,000 investment, I said no, GET CLOSER. I know in focal length limited situations the 7D will outperform (by a very small margin) the cropped 21MP 5D MkII/1Ds MkIII, and while I have not tested it against the 5D MkIII I would expect the results to be similar. To summarize that last sentence, I know in focal length limited situations the 7D will perform better than a cropped FF image, though not by much and certainly not as many as the pixel numbers would have you believe. I also KNOW, ALL PIXELS ARE NOT EQUAL, to compare one 7D pixel to one 5D MkIII pixel is moronic, it just doesn't work like that.
I agree, one needs to get closer. But in practice, there are limitations in doing that. Birds infrequently just sit still and let you get as close as you want. There IS an argument for buying better gear. It may not be the best advice for someone in chasinglights position, but it is not an invalid argument either. There are also consequences of getting closer. There is a zone within which one is closer to the bird, but also affecting it's behavior. If all you have is a 400mm lens, then either you deal with the behavioral changes, wait long enough for those behavioral changes to subside (which may never occur), slap the lens on a sensor with denser pixels, or get a longer lens.
We disagree about the "by a very small margin" part. All sensor pixels may not be equal, but that doesn't really matter. One only has to look at the two photos at full size to compare sharpness. If one reduces the resolution of one image from its original size, THAT makes for an unfair comparison. You are converting your bias against the 7D, the notion that its pixels only give it a "very small margin" benefit, directly into actual image comparisons. If you are going to scale for comparison, scale them both to the same size, don't scale one and leave the other unscaled.
In focal length limited situations, as this one is, per pixel comparisons are worse than useless, subject magnification is THE ONLY FAIR comparison, it is the only relevant metric for comparison of output. It maintains equivalency, you are comparing like with like. How do you adjust for different DOF figures if you compare on a per pixel basis? How do you adjust a sharpness figure when you magnify one image more than the other? You can't! Compare same magnification and you get a true comparison, you know what will look better in print, on a screen, or any other end use output.
Again, I disagree. As a matter of detail resolved, for example feather barbs, pixel peeping WILL show a meaningful difference. That difference may or may not matter for the artists final choice of presentation. If the image is shrunk and uploaded online, and that is the only thing ever done with it, then sure...per-pixel comparisons are effectively meaningless. On the other hand, if you scale up a heavily cropped 5D III image against a lightly cropped 7D image, and print at 16x24, then the 7D's resolution benefit IS meaningful. Per-pixel comparisons...or rather more realistically comparing both cropped images at full size, is an entirely valid way to evaluate IQ.
I am not even considering anything like a scientific test here, either...it doesn't take much to see improved sharpness with a little bit of eyeballing. I'm not talking noise here, either...just sharpness. The 7D image may indeed be considerably noisier in smooth OOF backgrounds, however even a noisy 7D image can still be razor sharp in the detail areas where it matters. Noise is also considerably harder to see in a print, so the greater resolving power of the 7D will have a meaningful impact on the sharpness of the final print. The 5D III noise would likely clean up considerably better, but the improvement is going to be less visible in a print than the sharpness factor.
As for DOF, from a technical standpoint, you are correct. From a practical standpoint, it usually doesn't matter. Unless you have a DOF issue such that a critical part of your subject is affected...for example the end of a birds bill ends up out of focus...that matters. If the important parts of your subject are in focus, at least in bird photography, DOF usually isn't a make or break issue. More of the butt end of a bird might be more blurry with one camera over the other, but if the eyes, bill, and a sufficient part of the birds head or body are sharp and clear...that's what really matters.
Anyway, I don't want to antagonize you further. You and I will likely never see eye to eye on the 7D/resolution issue (or, for that matter, the pixel density/resolution issue for any set of cameras, now or in the future). We disagree. I guess we just agree to disagree.