Although photographic printing by contact is the simplest procedure that could be devised for the purpose, there are several good reasons why printing by optical projection is often preferable.
By optical projection we can secure any desired magnification or demagnification, and thus make finished prints of any desired size from the whole or part of a negative. The development of the miniature camera would have been impossible without enlargers to provide prints of a useful size. Moreover, enlarged prints appear much more natural than contact prints because their center of perspective lies closer to the observer's eye.
In addition to this, projection printing gives the operator easy control of the exposure by âdodging,â and it enables one to correct the effects of a tilted camera by suitably orienting or tilting the easel. Projection printing has some further advantages: for instance, the negative may be suspended out of contact with other matter to avoid damage to a delicate film and to avoid the Newton's rings and dust spots that arise when a film is clamped between glass plates.
Online access to SPIE eBooks is limited to subscribing institutions.