The 40D has a sensor size that is smaller than a 35mm frame of film. Nearly all DSLRs do as well. The only exceptions are the the Canon 1DsMII & MIII, Canon 5D and the new Nikon D3
That means that you get the effect of additional magnification because of the smaller image circle. That magnification is 1.6x the focal length on his camera. Your 1D is a 1.3x crop.
That means that on your camera the 16-35 really behaves like a 21-45mm lens on a 35mm. On his 40D, it acts like a 26-56. The 12-24 that I reference behaves like an 18mm lens on that camera, which is quite a bit wider than your 16-35. Don't get me wrong, it's a great lens, just not what he's asking for.