Tilt and shift

[nellyleelephant]

So........Tilt and shift.....

Why and when would you use one? Apart from the fact that they seem to give edge to edge sharpness, why would you choose a T&S lens over a standard prime or zoom.

[markmullen]

You use the Scheimpflug principle to give an apparent huge depth of field without stopping down using front tilt. Actually what you're doing is moving the plane of focus from being parallel to the film plane, or sensor, to wherever you want it, in landscapes for example you can have the nearest foreground right through to the distant mountains (or whatever) sharp without going into the realms of diffraction with tiny apertures. On larger formats that is especially useful due to the shallow depth of field they bring.

You can also use the tilt to go the other way and give an apparent very very shallow DoF, the toytown look that it popular, you can use that for portraiture to give the look of shallow DOF when you can't use the lens wide open (for example when you're shooting in bright sun, or with flash).

Shift (technically rise, fall and shift) is used in architectural work, usually front rise, to avoid converging verticals. Shift is like rise and fall but left to right, ideal for photographing interiors when you've got a mirror, you can stand to one side and shift the lens so you're not in the reflection.

[RobDickinson]

I use tilt to lay the plane of focus down along the ground to provide more dof at a sensible aperture than you would normally get.

I use shift primarily for stitching.35mmm sensor is 36x24, 12mm of shift gives you a 60x24 or 36x48 sensor with very little downside and simple stitching.