I'm curious to know what the IQ differences are between these two options when using a crop sensor camera such as the 20D with 8MP. Does anybody have both of these lenses with an extender? The IQ differences when on the 1Ds Mark III are clear; 400 prime wins in sharpness hands down. Will the differences be similar when using a 20D? Or will it not be noticeable?





Thanks,
Derrick