Tilting and shifting either lens and/or film plane was commonly used in the old days with large format cameras (Ansel Adams camera for example). In today's market, the film or sensor plane can not be moved any longer in the DSLR or medium format cameras. Photographers need to rely on so-called manual focusing tilt/shift prime lenses which allow up and down or sideways movement of the lens plane as well as tilting it. Common focal lengths for tilt/shift (T/S) lenses are 17, 24, 45, and 90 mm for cropped and full frame DSLR cameras. But who can make use of T/S lenses, what are they good for?
Wide angle T/S lenses are commonly used in architecture and landscape photography, but also with longer lens focal lengths for closeup photography of jewelry, even sometimes for portrait work. Architectural photography commonly makes use of the shift function in the T/S lenses: Falling lines of tall buildings can be reduced or fully avoided. The image plane and therefore the focus are kept parallel to the subject. There are post processing programs out there which correct falling lines in photos taken with regular lenses, too. This gives a more natural look very similar to a photo taken with a T/S lens, but it will crop the photo without keeping the regular film or senor proportions of the negative or RAW file.
Shifted vertically, lines can be kept parallel to the subject which leads to a more natural look as seen in the central University building at Princeton University below. This was taken with Canon's 24/3.5 T/S lens where the lens was shifted 10 mm up.
Instead of shifting the lens vertically, sometimes it is useful to have it shifted horizontally to create a distortion-free panorama photo. The crosswalk photo is a stich of three single photos - one shifted horizontally fully to the left, one center one (not shifted), and one shifted to the right. Have a look at the pillars - they are all straight, only the one far left is bent a bit due to the lens angle towards the subject. By stiching three 24 mm T/S photos together, the field of view is similar to a 14 mm lens! Landscape photographers apply this technique to create a natural looking super-wide angle view.
Lens tilting can create the "miniature effect" - focusing on one specific subject in the frame, and making the surrounding area blurry. The photo below taken at the Red Mill in Clinton, NJ shows this effect - I used the few mm tilted 24/3.5 T/S lens in combination with a 2x teleconverter making it a 48 mm f/8 lens. The shallow depth of field surrounding the fisherman in the middle of the photo was only created by tilting the lens out of its focal plane following the Scheimpflug rules.
The lens was also shifted a bit up to have the sensor plane parallel to the corner wall side of the Red Mill behind. Combination of shift and tilt can work nicely, but it takes a bit trial and error to get used to. A camera equipped with LiveView is very helpful here since it allows you to see instantly the final composition of the photo.
Instead of creating more shallow depth of field, tilting the other way allows much deeper depth of field at a fairly low aperture number (more wide open aperture). The photo with the old barn in Valley Forge Park, PA is an example for this: To have both the brick wall in the front and the building in the back in focus, normally you would need a small aperture like f/22. This shot again was taken with my 24/3.5 T/S lens, but at an aperture of f/4.5. Tilting and shifting the lens in the right directions allows to focus both background and foreground reasonably sharp and keeping the sensor plane parallel to the structures. If you look closely, you will see that the plant branches in the middle are unsharp - the result of the Scheimpflug rules since the depth of field is no longer horizontally aligned when the lens is tilted!
T/S lenses take some patience and experience to get used to. You always need a tripod to work with a T/S lens. Also they do not come with AF. In case the lens is shifted and tilted, I recommend checking the focus confirmation with the enlarged area finder in LiveView. Exposure also changes with the shifted direction of the lens. But main disadvantage is the price - they still cost about $1K as used and older lens versions. Latest new T/S models are at least double this price. They have less vignetting and a better rotation system of tilt and shift being parallel or perpendicular. I am still using the older (first) version of Canon's 24 mm T/S lens, and so far I am fine with it, too. If you once get used to T/S lenses, you will always carry one with you if composition allows to use it for.