Why are there no long EF-S lenses?
Consider an EF lens such as a Canon 400mm f/4 DO on an crop factor camera such as a Rebel or a 7D. My understanding is that the lens produces an image circle substantially larger than the sensor. (99% sure of that.) The extra light is effectively blocked somewhere in the camera. Not deliberately, but it just doesn't hit the sensor at all.
Is the light path such that one could place black tape around the edges of the lens aperture without effecting the final image? I.e. could we block off the light that won't be used anyway on the lens aperture? (and if not, why not?)
And if that is true, why does nobody make a long lens for EF-S cameras that produces the same light with a smaller size and aperture? I.e. why is there extra glass and weight we don't need? Is it simply that there's not a market for long lenses only for crop factor cameras? Or is there some part of the physics or lens design I'm misunderstanding?
There are EF-S lenses with smaller image circles in the under 100mm range. Why is there nothing in the 100mm+ range?