Focus & AFMA Tests: Use "Spot AF" or "1-Point AF"?

Started Dec 19, 2013 | Discussions thread
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Focus & AFMA Tests: Use "Spot AF" or "1-Point AF"?
Dec 19, 2013

On the Canon 5D Mark III, should a user testing a lens for focus & AF micro-adjustment be using "Spot AF" or "1-Point AF" when shooting the target? In particular:

1) If I use the LensAlign ruler and properly setup my camera so that I see the red alignment dot through the hole, should I be using Spot or 1-Point to shoot that target?

2) I was reading Focal's PDF documentation and they specifically say that Canon cameras should use 1-Point and not Spot, but they don't give a reason why. Can anybody explain why?

3) Could anyone please explain in general how using either Spot or 1-Point could influence these lens focus tests? If there's a "correct" choice, what is the reasoning/mechanics behind how the "incorrect" choice might corrupt the test results?

4) When the lens is set to manual focus, is there any difference whatsoever in choosing Spot/1-Point/4-Point/9-Point/Zone/Auto/etc.? I thought I'd ask because on page 112 of the 5DM3 manual, the section called "Manual Focusing", it says "with 61-point automatic selection, when the center AF point achieves focus, the focus confirmation light [dot] will light up." This line gave me a little bit of pause because by mentioning the 61-point automatic selection system in the "Manual Focusing" section of the manual, they seem to be implying that the AF system is somehow still in effect?

5) Would a difference in ISO affect AMA results? For example if you shoot indoors and need to bump the ISO up a bit, will doing so skew/corrupt the focus tests?

Any clarification would be appreciated. Thanks!

Canon EOS 5D Canon EOS 5D Mark III
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