Zoom Enlarging Lens

Photographic enlargers intended for amateur or small volume use have a variable total conjugate distance distance because they use fixed focal length lenses. For high volume photoprocessing this is inefficient and a zoom lens is normally used to allow the total conjugate distance to remain constant. This month's design (see Fig. 1) is a two group negative-positive zoom with a fixed total conjugate distance that is suitable for making small enlargements of negatives ranging up to 56 X 41.5 mm (6 X 4.5 cm).

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