Corner tests for 16-35 f/4 vs. 16-35 f/2.8 (v.1) vs. 24-70 f/2.8L II

Started Jul 4, 2014 | Discussions thread
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halfwaythere Contributing Member • Posts: 848
Re: Corner tests for 16-35 f/4 vs. 16-35 f/2.8 (v.1) vs. 24-70 f/2.8L II

Just another Canon shooter wrote:

Abu Mahendra wrote:

I understand it alright. The idea is very simple. If one wants to Know how a lens resolves in any given spot, one focuses the lens on that very spot. If one wants to Know how a lens resolves at point X, one does not focus at point Y. It ain't I who does not get this elemental concept.

What you cannot understand, even after I explained it in other threads, is what to do when you want to maximize the sharpness across the whole frame. It may sound very weird to you, but this is what the majority of the UWA users want. Get it? You want the corners, the center, everything in focus.

Field curvature can easily ruin the corners. The sharpness in the corners may depend heavily on how far you focus (in the center). PZ explains in here. In such cases, the solution is to focus close. Here is a picture that says it all:

source: PZ

If you have further questions, write to Klauss.

You should've kept reading:

This "workaround" is viable at small to medium aperture settings but it does naturally fail at large apertures where the depth-of-field is not sufficient for such an approach anymore.

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