Crop FactorWe mentioned crop factor a few days ago in our lens compatibility post series, and wanted to give an actual visual reference for what is happening so that you can better understand it.
We also stood and center-focused on the exact same spots in both images.
This is something to keep in mind when purchasing a non-digital designated lens to use on a digital SLR body that has the smaller APS-C size sensor. In this case (and using Canon as an example), the 50mm EF lens no longer acts as a true 50mm lens on the 40D. If you want to obtain a true 50mm and own one of the APS-C size digital SLRs, you would want to purchase a digital EF-S lens that is in the 50mm range, or an EF lens that is a smaller mm, or wider angle lens to start with.