Tilt-shift photography refers to the use of movements of the lens on small and medium format cameras by combining the rotation of the lens relative to the image plane, called tilt, and the movement of the lens parallel to the image plane or line of sight, called shift.
TILT IS used to control the orientation of the 'plane of focus' (PoF), and hence the part of an image that appears sharp; and to change the line of sight to minimise the convergence of parallel lines in the subject’s shape. The inset picture is the illustration of the change in the line of sight with a tilt in the lens for photographing the kite.
Another simple similar technique is called “tilt-shift miniature faking” is a process in which a photograph of a life-sized location or object is manipulated so that it looks like a photograph of a miniature-scale model by taking the picture from a height and combining both tilt and shift.
In order to compose the picture by experimenting with various combinations of the camera tilts and lines of sight, see the composition on the screen of a digital camera and find out when it becomes interesting with minimum convergence effect and then click. Especially for product photography, the selection of proper camera tilt and shift is very important.