I have been asked before how wide the 15mm fisheye is compared to the 16-35 but never had any good tests to show it. I had similar shots taken from the same place but never done on a tripod from the exact same place. I also wanted to see the difference between full frame and 1.3x Heres the pictures. All taken from the exact same place at the same ISO, shutter speed, and aperture. First, heres a 15mm fisheye compared to a 16-35 @ 16mm. 15mm 16mm Now, heres the comparison of the 15mm on a FF-vs-1.3x body and the 16-35 on a FF-vs-1.3x body 15mm 1D 15mm 5D 16mm 1D 16mm 5D Hopefully this helps to visualize the difference for anyone wondering.