Controling Perspective with a Tilt Shift Lens
A tilt shift lens is the lens that is needed to be used when working with tilt shift photography. These specialized lenses give a photographer greater control over the perspective of his images than is possible to achieve with ordinary lenses. They can be used to either correct perspective errors due to camera position or can be used to accentuate them for artistic purposes. It should be noted that tilt and shift are actually two independent functions that are achieved in one lens.
In an ordinary lens, the image plane, lens plane and object plane are all parallel to each other. This results in objects that are in sharp focus, all being at the same distances from the camera on an imaginary parallel line from the lens. When you change the tilt of the lens, you end up causing the lens plane to move so that it is no longer parallel to the image and object planes. This results in the line of focus no longer being parallel to the lens. An object that is 15 feet away from the camera and an object that is 30 feet away from the camera can both now be in sharp focus, providing that they rest on an imaginary line that is parallel to the lens plane. This concept is referred to as the plane of focus.
When using an ordinary lens, if your subject plane is parallel to your image plane, then parallel lines in your frame will remain parallel. But, if the image plane is at an angle to the subject plane, then it will create a false perspective that the lines will converge as the distance from the image plane increases. Using the shift movement in a tilt shift lens will correct this.
The shift moves the image plane without moving the camera. The lens is allowed to shift so that it can become parallel to subject plane. This can allow you to make the lines parallel again. Or, if you like, you can shift the lens in the opposite direction to push the convergence of the parallel lines for an artistic effect.
Creating Panoramas with Shift
If you want to create breath taking landscape panoramas, then a tilt shift lens is a tool that you should invest it. You can create seamless panoramas with an even 'X' axis by changing the shift without having to move the camera. Your final result will look like one long photo instead of a compilation of several photos joined together, thanks to the continuity provided by this special lens.