See my Aug 3 comments on the useful and creative things one can do with with a “tilt” lens. Among other things, the plane of sharp focus can be tilted to be non-parallel to the sensor, which means that wide open at f/2.8 it’s possible to make crisp images from near to far. Depending on the angle, this can mean a sacrifice of sharpness in other areas, a great creative effect (the glass is half full). The fence image below is just as sharp at the bottom as the top at f/2.8, something impossible with a non-tilt lens.
The difference in depth of field achievable using tilt is enormous.Both images taken at f/3. In this example, the tilt operation provides depth of field roughly equivalent to stopping down to f/16, probably f/22. The “tilted” image renders sharp results even at f/3. By stopping down to f5.6 - f/8 (this subject matter is not completely planar), the tilted image would be of of a quality impossible to achieve without tilt. (A non-tilted image taken at f/16 or f/22 image would suffer badly from diffraction). Get the Nikon PC-E Micro-Nikkor 45mm f/2.8 ED at BH Photo. See also my first impressions of the Nikon PC-E Micro-Nikkor 24mm f/3.5 ED.