A frequent goal in the design of photographic equipment is a reduction in its overall size and weight. This is particularly true with regard to portable cameras where a reduction in size and weight allows the camera to be more easily transported, as well as more easily manipulated during photographic use.
A significant factor which dictates the size of photographic equipment is the total conjugate distance, i.e., the distance measured along the optical axis between the object and the image. The total conjugate distance (TC) is a function of the focal length of the lens. In a camera, for example, which houses both an object field such as data card, and a receptor surface, such as photographic film, the ability to reduce the total conjugate distance is important in reducing the overall size of the camera.