That's a good point Leif.
I've been pondering this possiblity.
I'm intrigued about the use of full aperture to aviod the err99 situation, as Adey suggested.....I wish we'd thought of it before getting rid of the sigma 28-200.
We should have played at blanking some of the contacts off too....maybe the AF would need to be blanked off too??
I believe that the very early digi bodies like the D30 and D60 used earlier chips than the 300D,350D,400D etc.
I can fully understand the reasons and reasoning behind progress.....It just seems very strange, somehow wrong, that for example, I can fit one of my elderly manual Tamron adaptall lenses to wife Jacky's canon digi body, but full auto purpose made EF mount lenses from not half as long ago are no longer compatible.
Certainly from our perspective, many of my higher magnification lenses Jacky feels are too heavy for her. A lightweight 400mm would seem to fit the bill better to extend her shooting range beyond the 100-300 she uses at the mo.(ironically more often than not used at full 5.6 open aperture)