As a point of fact, the D100 is a crop body, with a 1.5x factor, so it is very similar to my 40D if not quite the same. You're right about the low density, at 6.1 MP. Certainly my Canon's resolution is much higher. A 400mm on the D100 is effectively 600mm, whereas a 400mm on my 40D is effectively 640mm. Different, but not hugely.


Good point about the AF system in my 40D versus the 1-series. I just remembered I have a test subject in the form of a Nikon D200 (a loaner from a friend before I bought my D100 to use with the Nikon-mount Sigma that I got as a gift), so I will be able to see for myself what effect a different body has, all else equal.


You're right about the MFD probably not being important, but it is ironic that I have enjoyed the Sigma's macro capabilities, as it is a APO TeleMacro version which is good for 1:3 magnification. Takes great, frame-fillingflower pics with nicely blurred background almost certainly BECAUSE of the focal length.


I just need a night job, I guess.


P.S. Brent, I am sorry if we sort of hijacked your thread. [:$] It is still about the 300mm f/4, though. []