Condensers, their Contour, Size, Location and Support
C. Francis Jenkins · Transactions of the Society of Motion Picture Engineers · 1916
Surprisingly little literature has been written on the subject of condensing lenses, and none at all with regard to their use in motion picture projecting machines. Investigators outside our own art have so far failed to observe that the problem is not the same in a motion picture projecting machine that it is in a stereopticon lantern, a difference resulting from the necessity for the use of a shutter with the motion picture projector.