Quote Originally Posted by bob williams
Recently, I was revieweing Bryan's reviews of these lenses and noticed that the ISO 12233 Crops seem to be much sharper on the 500 than on the 600.

Agreed. The difference disappears by f/5.6, but wide open it is more apparent if you stick a 1.4X or 2.0X TC on there:


500 vs 600 f/4


500 vs 600 f/5.6


500 vs 600 with 1.4X TC


500 vs 600 with 2.0X TC


It's possible that it could be explained by some unit-to-unit variance on these lenses. Another factor to keep in mind is that the 600mm would be sharper if the 500mm image were cropped digitally to match the AOV.


They are close enough in image quality that I wouldn't let that weigh into the the purchase decision. Weight and size are more important factors.