The camera technique of a professional photographer is dependent considerably on the lens used. Therefore, the choice of a really fine lens is perhaps the most important decision with respect to equipment that a photographer is called upon to make. His future photography rests not only on the quality of the lens itself, but also on the suitability of the lens for the tasks it is to perform. The drawing and perspective of the image formed by a lens depend upon the point of view—the lens-to-subject distance—not on the lens. Yet, the area of the scene covered and the size of the image are functions of the lens, and these, in turn, often are the factors which determine where the camera is placed. The covering power and the focal length of lenses therefore regulate their suitability for a given purpose.
In addition to these factors governing the choice of a lens, there are the limitations imposed by the bellows draw of the camera and the desired swings and other camera adjustments the photographer may wish to impose on the camera image. Thus it is that the choice of a lens and the problem of camera swings are interdependent.