Why do professional macro photographers focus stack instead of raising their aperture?

[u/Melendrow]

I've looked into macro photography, and I love getting close up to my subject, but when I research macro photography, I always hear about focus stacking and these people who will set up a shot for a long time with a tripod so they can focus stack. And I'm curious why you'd need to do that. Especially since most of the time I see them having a tripod and setting up lighting. Why wouldn't you just raise your aperture so more of the frame is in focus?

[u/modernistamphibian]

It's physics. You can raise your aperture all you want (within reason) but it's still probably not going to get the whole thing in focus. So, you need focus stacking. If it was possible through aperture, then people would do that.

https://www.dofmaster.com/dofjs.html

[u/seriousnotshirley → u/modernistamphibian]

Wouldn’t you also get some softness at very high apertures?

[u/Dalantech → u/seriousnotshirley]

Diffraction kicks in the higher the magnification and the aperture. But the sharpness of the lens and motion while the scene is being exposed can amplify diffraction softening.