Just to avoid confusion, I realize I do need to make sure my terminology is somewhat accurate. By "optical quality" I referred to the capability of a lens to resolve details and produce sharp and crisp images. I wonder whether I am wrong in this?


Ok, yes, I understand the physics behind this.


Ok. So, speaking in theory, would there be a difference between a Macro and a non-Macro lens, in this specific regard, holding all else constant?

Would it be correct - I am just guessing here - to say that a macro lens would limit its max aperture in order to gain something in terms of little-diffraction at lower apertures, assuming little diffraction is what you want to obtain crisp and detailed macro pictures? In other words, I am supposing that If I want to build a lens that is very good for macro and therefore with as little diffraction as possible, I may have to limit the possible aperture available? For example, a Macro lens would be excellent at f/2.5 and really bad at f/1.8, so I have to limit it at f/2.5, while a non-macro lens is just good at f/2.5, but not bad at f/1.8, so I allow aperture f1.8?


Why is that? Not good in what way?

Again, thank you all guys. I am learning so much. This is just great!!