Comparon 150 mm F/5.6 Schneider-Kreuznach

Lenses designed for magnifiers have a special design, because, unlike shooting lenses, their optical calculation is performed not for "infinity", but for finite short distances lying in the range between the main and double focal lengths. They differ from other projection lenses in the presence of an iris aperture, which allows you to increase the depth of field and adjust the exposure when printing.