Softness on the edge

Started Feb 22, 2021 | Questions thread
MitchAlsup Veteran Member • Posts: 5,462
Re: Softness on the edge

Kendunn wrote:

MitchAlsup wrote:

Kendunn wrote:

Getting a weird, overly soft edge on rare occasions, not sure whats up. Canon 5DS with a 17-40. The example posted shows the top 20% of the frame is way too soft, but the rest of the frame is reasonably sharp, including the bottom. It was shot at 35mm, f/7.1 off of a tripod, I think it was 1/20 at ISO 100. Most of the time images are fine. Loose element?

You do realize the stuff at the top is more than twice as far away as where the tree emerges from the ground !! do you not ?

My guess is that the lens accommodation (near-focus to far-focus) is the culprit. Your choices are to push the aperture slower and get diffraction across the whole image or to widen the aperture and deliberately take the top OoF.

Thanks for the input, but a 35mm len @ 7.1 focused at 20' will have a DOF to infinity. This tree was probably 100' away and what was focused on. You can also look close at right side of the image and see trees that are sharp at their base but very soft at the top.

If you change "will have" to "should have" in the first sentence I can agree with you.

Using a 17-40 lens at F/7.1 is not the same as using a 35mm prime at F/7.1 ! Plus primes are better off axis than zooms. The 5Ds may be out resolving the edge of what the 17-40 lens renders.

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