I prefer the summaries that Klaus on Photo Zone produces. Here are results for a sample of the Nikon F1.8 AFD lens:
http://www.photozone.de/8Reviews/lenses/ni...50_18/index.htmAs you can see, edge performance is still improving at F8, and might well improve more at F11, though by then on-axis performance is dropping. Note that Klaus used a D200 for his measurements.
I performed some tests with a 200mm Nikon lens on a D200, and the centre and edge sharpness were superb between F4 and F11, with a tiny softening at F16. I have heard similar comments from others. Klaus has also tested the Nikon 60mm F2.8 micro lens:
http://www.photozone.de/8Reviews/lenses/ni...60_28/index.htmAs you can see, that is good to F11, with a slight softening at F16, and a slight edge softening wide open.
"For this reason, when comparing DoF of the image or print, it is only sensible to compare images of the same field of view. When we do this, the crop factor of 1.6x (in relation to the 20D and 5D) plays a role in most of the calculations. The 5D sensor is 1.6x larger in either dimension, than the 20D. The focal length of lens that produces the same FoV is therefore 1.6x longer (for the 5D) and the f stop # on the longer lens that produces the same DoF is 1.6x larger."
Thanks for pointing out the DOF ratio.
Your paragraph is very interesting, but the first part is a little contentious, at least with my style of photography. In practice we might have a 200mm macro lens which we use on a 5D and a 20D. In that case when using the 5D we will move closer to create the 'same' image. Now of course the image is not the same, as the perspective is different. However, DOF is a function of F ratio and image magnification only. Hence in these two situations (photographing a dragonfly that fills the frame say) the smaller sensor will have the larger DOF.
This is probably a significant advantage of smaller sensors for long telephoto photos e.g. birds. Not only does the 20D have a telephoto effect, it also effectively increases DOF.
Leif