What focal length lens is this lens?


Senior Team Emeritus
Premium Member
Mar 29, 2003
Know I have posted this formula in the past but otherwise fair game to all before I check my notes or spare lenses to compare with:

Got a 100+ year old set of 3.1/2" lenses to a lens accessory on a starlight sciopticon assembly that does a lens train in front of the wheel in refining the image. Page 18 in the lens train to Chicago Stage Lighting Co. Catalogue (CB WiKee) - in this case by Kliegl as a maker of this specific lens train.

Lenses measer 3.1/2" wide by 7/16" thick when standing on the convex side.

What size of Altman 3.5Q lenses - given these measured are toast should I replace them with?
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