Given that the XTi has 10 MP, the 5D only manages about 12% more resolution for a given subject size and at the same magnification. Unless the subject was larger than about 21x32, the XTi would still put more pixels on the subject all the way down to 1:1 on the 5D.
At the same magnification, true, but if I'm shooting say a butterfly and it is 24 by 36 mm to fill the frame the 5D would have to be at 1:1, but as the object is larger than the sensor size of the XTi, one would have to shoot at a magnification something less than 1:1




My boss also wants me to become a dive con (and I want to eventually become an instructor) so I need to know how NOT to kill my students
