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 p.2 #20 · 7d autofocus worked fine, now not! | |
TeamSpeed wrote:
Finally, to your comment about 100% views, I will have to respectfully disagree. One of the single large mistakes people do make is to take each and very image from different bodies and then zoom in to 100% view to compare. That is really quite inappropriate. The only way I do my check for IQ is to first process the image and then resize it to the print size I expect to make at the DPI I need, then I zoom to 100% on that image. If you just take a 7D image and view 100%, it will undoubtedly show imperfections that won't please, however they won't show up on prints, so it is a false positive on the IQ of the image.
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I couldn't agree more with the statement that I quoted above. With the 18 MP sensor of the 7D, when you are looking at a 100% crop, you are looking at a very, very tiny portion of the total image. The images that you posted in your earlier post are a great example. When you look at the ISO 6400 shot and look at the large version to which you linked, the noise appears to be horrid. However, when you look at the full image, it may not look as clean as one shot at ISO 200, but it looks very good, and I'm sure that it would print quite well at a reasonable size.
Any comparisons of images from two cameras with different pixel count or density comparing both at 100% is a completely invalid and meaningless comparison that will always make the camera with the lower pixel count or density look better than it should. If, for example, you compare a 7D image to, say, a 1D Mark II image both at 100%, the comparison might well make the 1D Mark II look better with regard to noise. But, because the 1D Mark II starts out with fewer than half of the pixels that the 7D has, each 1D Mark II pixel is going to have to be enlarged by twice as much to create a final image at any given print size, and, the more you have to enlarge each pixel, the more you are also going to be magnifying noise. If, on the other hand, you compared images from both cameras at comparable output sizes, I'm confident that the 7D image would be the clear winner. Even if you were shooting with a 1DX, which would seem to have a huge noise advantage over the 7D, if you have to crop a 1DX image down to, say, 4 or 5 MP to get the same field of view as that from a moderately cropped 7D image, when you make a print (or look at the image on the screen at fit-to-screen view), each of those 4 or 5 MP remaining 1DX pixels is going to have to be enlarged so much and so will noise be magnified to an extent that much of the noise advantage of the 1DX will be lost. I routinely shoot my 7D at ISO 800, and, if I have to, I'll go up to 1600 for wildlife shooting. I find, though, that, if I can't get the shutter speeds that I want at ISO 800, that generally means that the overall quality of the light isn't good enough to create pictures that I'm going to be happy with regardless of noise. And, when I look for noise at 100%, in those images, I'm probably going to be alarmed, but, yes, it does disappear in an actual print or even in screen viewing at fit-to-screen size.
Les
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