Here is another test to show the difference between a full frame sensor and 1.25x crop sensor mounted with the 17-40mm EF L zoom @ 17mm focal length. 1Ds has the full frame sensor, the 1D has 1.25 crop factor. Once again I put the 1D image on a seperate layer in PS and then tweaked the size using the free transform tool to get it to line up with the 1Ds image below it. Also both images are presented at 800 px below for another comparision.