I think I am understanding what you are asking now. Since the original photo was 4672 pixels wide and covered 2.5mm, the pixel size was 0.53 um. When I uploaded the original file to flickr, the site resized the photo and did not keep a copy of the original size. I am sorry to say that I don't have the original.
Tom
Originally posted by falconeye I wondered if you would understand what I mean.
A pixel with a K20D/K-7 displays 5µm at 1:1 and 0.5µm at 10:1.
However, if you're downscaling to 1024 for the web, this becomes 23µm and 2.3µm resp.
You may still call it 10:1 but it is meaningless. A 3x2px photo at 10:1 would have 0.8mm wide pixels and
stll you would call it 10:1 ...