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ahender wrote:
So all factors being equal, a 7D mk II image and a 7D image would appear equally sharp when taken in AISERVO mode.
An "almost" in focus image will look softer than a "sharply" in focus image. There is almost alway some variation from "perfection" or peak sharpness.
Older cameras had a lot more variability in their auto focus systems. The 7DII is much more accurate than the 7D.
So in AI Servo mode, the few "absolutely best" images from the 7D won't look much different from the best images on the 7DII. But a large percentage of images will look better on the 7DII.
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Here is Roger Cicala's comment on the 7DII:
OK, I have to admit I really like the 7D Mark II. I didn’t want to because it wasn't what I wanted. I wanted to see the new Canon chip foundry that would be cranking out high-resolution sensors. But despite wanting to hate the 22-megapixel APS-C camera, after a fairly short exposure to the autofocus system, I have to admit I like it. There’s just something about getting every shot in focus every time that’s appealing to me.
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For background, you might read this article from earlier this year:
Why You Can’t Optically Test Your Lens with Autofocus"
http://www.lensrentals.com/blog/2014/02/why-you-cant-optically-test-your-lens-with-autofocus
For more detail, you might read this article from 2012. And the whiole series if interested:
http://www.lensrentals.com/blog/2012/08/autofocus-reality-part-3b-canon-cameras
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From the last article, you'll notice that the standard deviation (SD) of the variance in the auto focus on the
7D - is 41
5D3 - is 17
1Dx - is 17
The 5D3 & 1DX auto focus systems are much more accurate, leading to a much higher percentage of "acceptably sharp" images.
The 7DII seems to be as good as the 5D3 & 1DX for accuracy. It might also better them in some instances, being a few years newer, and having 150K pixels and IR sensitivity in the metering system, for example.
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