DoF may not exist...

Started 3 months ago | Discussions thread
JimKasson
MOD JimKasson Forum Pro • Posts: 35,343
The test explained, once more, with feeling
3

Greg7579 wrote:

JimKasson wrote:

DMillier wrote:

I suspect expectation plays a part.

You have pixel peeped so many ultra sharp GFX shots now, that maybe your brain can't accept even the most conservative CoC values.

I gave Greg a test to perform to see if using a conservative CoC worked. That was a year ago. He has not performed it. So we don’t know if a conservative CoC fits with his perception. It would be a useful experiment, and would probably go a long way towards getting to the bottom of this.

I also posted examples of low-CoC images, and asked Greg to look at them. He refused to do so.

Maybe it's a bit like aliasing. Lots of people seem to be completely unbothered by the most obvious luminance aliasing because they don't know what they are looking at. But once seen it can't be unseen.

Perhaps in your case, your brain is now so finally tuned to absolute sharpness that you can no longer tolerate a CoC that most people are fine with. When diffraction is doing the softening, perhaps it does so in a way that affects all the pixels everywhere by the same amount, so the tell-tale gradual fall-off of insufficient (for you) depth of field your brain latches on to is not present.

Just thinking about the "other things" that provide an explanation beyond the normal science.

You are a pixel peeper but it would be interesting to find out whether you see the same effect in prints.

Jim, I have no idea what you are talking about. What images did I refuse to look at? And the test you keep talking about makes no sense to me. Explain it to me again. I go to a football field and shoot at ten targets

I said nothing about ten targets. You shoot one shot (or, much better, several if you want to be able to make sure you don't misfocus and invalidate the results). You pick the shot where the 100-meter-away object is sharpest. You look at the 50-meter object. If geometric optics is right, it should be just a bit away from critical sharpness, I've explained this test to you at least half a dozen times.

Here is the explanation again:

Take a GFX 100 or GFX 100S. Attach a 45 mm lens. Set it to f/5.6. Focus on something 100 meters away in the center of the image. Check sharpness of an object 50 meters away close to the center of the image. It should be on the edge of critical sharpness.

I picked a CoC a bit over the pixel pitch.

and then compare them to what? I never understood it. But I'll do it when I get home if it is doable.

I'm not holding my breath any more.

But I'm not posting any comparison images.

And why not?

Here's an example of what kind of setup to use. As a bonus, it is also a equivalence demonstration.

https://blog.kasson.com/the-last-word/ff-and-mf-dof-compared-visually/

And the images linked to above are the some of ones you refused to look at.

Jim

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