How much sharpness is reasonable to expect at various zoom/crop levels?

[SCoombs]

Of course distance matters, the more air you're trying to look through the higher odds that it'll be worse due to normal impacts, even if there isn't huge temp differentials, etc.

The sharper the lens to start with, the less it's impacted by this (but all lenses are).

This makes sense.

It's not that I am suddenly getting great keepers of very distant tiny subjects where the zooms weren't doing this for me, but at least when I use the 500 I am definitely getting a much more defined edge and I can at least see things like feather details that are supposed to be there even if it's too small to really call "sharp."

 

[Cameron T]

This makes sense.

It's not that I am suddenly getting great keepers of very distant tiny subjects where the zooms weren't doing this for me, but at least when I use the 500 I am definitely getting a much more defined edge and I can at least see things like feather details that are supposed to be there even if it's too small to really call "sharp."

For the sake of discussion, let's say the 500pf can resolve a sharpness of 1000 of some unit.

The 200-500/180-600/etc can resolve say, 900 units.

Now, in the same conditions/etc shooting a bird 10 meters away they both lose 10% sharpness.

You go to 900 for the 500 vs 810 for the others.

You're still resolving more detail regardless because the lens is sharper to start with. There is, of course, a point where it becomes mush regardless of how sharp a lens is. Temp differentials are usually the biggest barrier here, and any time there's more humidity it'll also make it more difficult

 

[Robert S]

I don't know much about 'sharpness' other than stuff I read and my own personal gut feeling on an image.
Perhaps this is relevant to some degree: https://archive.org/details/advancedphotogra0000lang_m0q1/page/20/mode/2up?q=sharpness . In order to access the book it may be necessary to sign up to archive; it is free.

On pg. 287 of the book it says this:

"It is reasonable to forecast that eventually most still photography will be done by electronic means, but we will be getting our hands wet in ‘archaic’ liquid processing for some time to come. The essence of photography remains the making of pictures by light, and this will always rely, as now, on having ‘a good eye’. Your ability to see pictures, organize subjects, viewpoint and lighting, and decide appropriate image sharpness and exposure still remains vital. It matters much less whether you image onto an electronic chip or chemicals coated onto film."

Advanced photography​

by Langford, Michael, 1933-

Publication date 1998Topics PhotographyPublisher Oxford ; Boston : Focal PressCollection printdisabled; internetarchivebooksContributor Internet ArchiveLanguage English

 

[bleirer]

The human eye can be very good at comparing, I think. But there are factors that have to be controlled to get a a true apples to apples comparison. You have to factor in and equalize the viewers visual acuity, the image size, the pixel dimensions, and the viewing distance. These factors impact apparent noise, depth of field, and sharpness. Any image can be made to seem less sharp, more noisy, and have less dof if we get too close when viewing, magnify too much, look at too big of an image, or have less than 20-10 vision.