[Rolf]

With Canon... the "S" series... S standing for Small Image Circle - are designed to match APS-C (blame Kodak and Canon for that!) size sensors. As the image circle to sensor size is relative to that of the standard EF series lenses for full frame sensors, there would be no crop. So, the 10-22mm S series lens is the equivalent view of having a 16-35mm on a full frame... but if you have the 16-36mm on an APS-C 1.6x crop you would be out of the wide angle range with 25.6-56mm at the long end. The "S" series protrudes further back to get the lens closer to the sensor... (this is rubber protected) and would be such that it's ingress into the shutter box of a non APS-C body,would cause the mirror to strike it and jam. To avoid that the mounting reference ("S" series a white square, Ef series a red dot) are different and the "S" series will only mount on bodies with a white reference. The mirror being smaller will not come into contact with the protruding rear. Ef lenses (no protrusions) will mount on both reference bodies. Quoted focal lengths are always the relativity to the "old" film size of 24x36mm - full frame. so... 10mm-22mm is just that on an APS-c sensor but, relative to 24x36 it is 16-35mm exactly the same FoV - just a different way of expressing the same thing .Not sure if that makes sense to you? It was much simpler in days of 35mm film...

Kind regards

Rolf