Interesting - any real world tests to demonstrate this? When it comes to DOF, I'm not interested in logic or theory. I've seen too many flamewars that involve only theory and no actual field tests.
>Plus when you zoom out and crop you waste sensor resolution and photon gathering power...
I started digital photography on 2 MP. Then moved up to 8 MP. Then to 16 MP. From my experience, the difference between 8 and 16 MP is fairly small. The only benefit for me to go to higher resolution at this stage is the ability to crop and still get high resolution. Without cropping, I don't benefit from extra megapixels.
I'll concede the light per pixel point, though.
https://i.imgur.com/GtljNmg.png top is 50mm, bottom is 100mm
Why? The antialiasing filter and demosaicing destroy detail at a fixed scale relative to the captured image.
A few quibbles:
1. The goal is to maintain the DOF distance. For 100mm at f/32, if you go to 50mm, you need f/8.
2. The assumption is that the lens is as sharp at 100mm as it is at 50mm (on some lenses this is a terrible assumption).
I tried a similar experiment comparing 25mm with 50mm (f/5.6 vs f/22). You can see the results at https://imgur.com/a/ik6qe5K
To me, they are almost identical - with 25mm seeming a tad bit sharper. In a way, though, you're right - the difference is so small that I might as well shoot at f/22.
100mm at f/32 is the same as 50mm at f/8 only if you don't crop 50mm by 2x.
These are both excellent lenses, and at f/32 and f/16, optical quality basically ceases to matter.
Plus when you zoom out and crop you waste sensor resolution and photon gathering power...
Plus, even an expensive camera suffers at f/22. The only thing you can do is use tilt shift and an actual larger aperture.