The focus shift issue with the Canon RF 100mm f/2.8L IS USM Macro revisited in revised review

stevelee · Oct 17, 2021

At macro levels, the focus mostly a matter of choosing magnification. So if I am using a tripod, I use the focus dial for setting size, and the rail to focus. The added bonus (besides not driving one’s self crazy) is you are already set up to do focus stacking if you want it.

Chasing around insects is a whole ‘nother matter. Even then I have better luck moving the camera to focus rather than twisting a dial. And if someone can do that at 1.4x, he’s a better man than I.

Viggo · Oct 18, 2021

stevelee said:
At macro levels, the focus mostly a matter of choosing magnification. So if I am using a tripod, I use the focus dial for setting size, and the rail to focus. The added bonus (besides not driving one’s self crazy) is you are already set up to do focus stacking if you want it.

Chasing around insects is a whole ‘nother matter. Even then I have better luck moving the camera to focus rather than twisting a dial. And if someone can do that at 1.4x, he’s a better man than I.

Focus shift makes no difference in MF or AF, it happens as the aperture closes during exposure, so it will still be a problem. Not sure if you can use dof-preview and dial in focus based on that preview.

neuroanatomist · Oct 18, 2021

Viggo said:
Focus shift makes no difference in MF or AF, it happens as the aperture closes during exposure, so it will still be a problem. Not sure if you can use dof-preview and dial in focus based on that preview.

Correct. If you’re shooting at f/2.8 (with macro, unlikely), there’s no focus shift. If you stop down, there will be backfocus that goes away narrower than ~f/11, because at that point the DoF is sufficiently deep to encompass the backfocus. So if you usually shoot at f/14, focus shift is a non-issue. If you focus stack it’s also a non-issue even if you shoot wider than f/11 to avoid any softening from diffraction, provided you collect a deep enough stack.

stevelee · Oct 18, 2021

Viggo said:
Focus shift makes no difference in MF or AF, it happens as the aperture closes during exposure, so it will still be a problem. Not sure if you can use dof-preview and dial in focus based on that preview.

Yes,I realized later that my post somewhat missed the point. Otherwise, I meant what I said, for what that’s worth. I’ve never experienced focus shift as far as I could tell in macro situations, so it is not something I related to. I would think DOF preview should help on a mirrorless camera. On my DSLR, looking through a glass darkly is not likely to tell me much.

leadin2 · Nov 14, 2021

I used f/5.6 and f/8 with auto focus quite often, so EF L will stay with me longer. =)

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The focus shift issue with the Canon RF 100mm f/2.8L IS USM Macro revisited in revised review

stevelee

FT-QL

Viggo

neuroanatomist

stevelee

FT-QL

leadin2

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