Zoom Enlarging Lens
J. Brian Caldwell
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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