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

Started 3 months ago | Discussions thread
Just another Canon shooter
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Re: Love note to the nit pickers.
In reply to hotdog321, 3 months ago

hotdog321 wrote:

Seems to be some sensible (also some nit picky) discussion about the way I shot this test, IE: focusing on the center and examining the corners.

Yes, I am aware that I could manually focus on the corners of the image instead of focusing on the center. This would give a critical test suited to the lab, which is really nice sometimes.

But who the heck shoots that way?

So far, agree, and this is what I have been saying to Abu all that time - and that is why he is still chasing me from thread to thread trying to settle an old score.

When I shoot an image, I am focusing on a subject which may or may not be in the center of the frame. But I still want the corners to look as good as possible, especially when I am forced to shoot wide open at f/4 (events, low light, action, etc.)

Therefore I shot examples focusing on the center, but examined the corners. All the centers at f/4 look pretty good, which we expect. But the key is how the corners will behave when the center is sharp. Bokeh be damned, I want those corners to look crisp on a real assignment, not in the lab.

Here I am not 100% with you. If you have a main subject and you shoot at f/4, you probably want to maximize the resolution there. But if you take a panorama kind of shot, you want everything in focus. With WA but not UWA, people focus 1/3 into the scene, at hyperfocal distance, etc., but normally they would not focus at infinity. With UWAs, the theoretical DOF even at f/4 is so deep that you may say - why bother - just focus where the center point happens to be. Corners have their own behavior however, varying from lens to lens, so this is not that simple. You may have to focus at 2-3m, or past infinity, etc., depending on the lens. Because of the deep DOF in the center, the resolution in the center will not change much but the corners may improve.

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