That's actually how a lot of cameras work, particularly smaller consumer and prosumer ones with integrated lenses. The zoom position and focus position is work

That's actually how a lot of cameras work, particularly smaller consumer and prosumer ones with integrated lenses. The zoom position and focus position is worked out by moving the front and back elements of the lens, with a bit of adjustment so they track together properly. I actually have a nice old Sony V1E where the back positioner has failed (or become disconnected, possibly) so it never really looks right, and it would be too expensive to repair. It works great as a DV playback deck, which seems like a bit of a waste I guess, but repairing it would be about the same price as buying a working one.