As I understand things, and these are extremely simplified examples, tilt-shift lenses have two 'main' uses. Shifting the lens allows you to keep your camera parallel to your chosen subject but 'shift' it to capture those parts of your subject you would otherwise miss by not tilting the whole camera and throwing out the perspective. And tilting allows you to change the plane of focus without altering the angle of the film plane.
From what I can tell most (if not all) tilt-shift lenses 'shift' in landscape mode and 'tilt' in portrait mode. And I believe it is possible on some models (Canon's TS-E for example) to dismantle them and rearrange the mechanisms so they will tilt and shift in the same plane.
But why do they work in this manner? Why not 'tilt' in landscape mode and 'shift' in portrait?
From what I can tell most (if not all) tilt-shift lenses 'shift' in landscape mode and 'tilt' in portrait mode. And I believe it is possible on some models (Canon's TS-E for example) to dismantle them and rearrange the mechanisms so they will tilt and shift in the same plane.
But why do they work in this manner? Why not 'tilt' in landscape mode and 'shift' in portrait?