"Eric Miller" wrote in message
...
I went from the 10D to the 5D. When I had my 10D, I learned to like the
1.6x way of fooling myself into thinking my 400mm lens was a 560mm lens.
Now I am thinking of getting myself another birding camera and am trying to
figure out if there is a way to think of resolution as effective focal
length versus the 10D. So, for example, if I were to get a 7D at 18
megapixels how would that compare to 10D resolution wise in terms of what
focal length lens would I have had to put on the 10D to get a 5 inch tall
bird at 20 meters (or any distance) to be rendered by the same number of
pixels (one dimension only or my head will hurt too much) on the 10D that
it would be rendered on the 7D using the 400mm lens.

Eric Miller
www.dyesscreek.com

Both the 10D and the 7D are APS-C sized sensors, so your 400mm lens will
have a 1.6 FOV crop, so both will be similar to a 640mm (not 560mm). I never
work in pixel pitch in photography.