What is a Tilt-shift lens?

a tilt-shift lens lets you either tilt the front element of the lens vertically as if on a hinge, or shift it horizontally like a sliding door from one side to the other (usually the element can also be rotated 90 degrees to allow for horizontal tilting and vertical shifting). These lenses are pricey – they’re predominantly used by architectural and interior photographers as the shift function allows for the straightening of converging verticals, so buildings don’t appear to be ‘leaning over’ like they can do when using a wide-angle lens closely. By contrast, the tilt function changes the plane of focus.