enlarging lens

Definition: Optic designed to be suitable for making projection prints. * Features should include (a) flat field (b) very low geometrical distortion (c) no shift of focus with stopping down (d) correction for short object distances.
Enlarging advantages
For such specialised optics, enlarging lenses are actually more useful than usually thought. Even very average enlarging lenses make superb close-up lenses when used with a bellows attachment and they are the bee's-knees when it comes to making duplicate transparencies. Generally they are at their best used one or two stops from maximum. Modern designs are achromats or better and don't shift the focus on stopping down because they are very flat-field objectives, so the old precautions of focusing through blue glass and checking focus after stopping down are obsolete.

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