An Improved Condenser System for Motion Picture Projection
Lewis M. Townsend · Transactions of the Society of Motion Picture Engineers · 1927
At Present there are four types of illumination in general use for motion picture projection. They are as follows: (1) The straight arc with 4½-inch diameter condensers. (2) The mazda lamp with condensers. (3) The high intensity arc with 4½-inch diameter condensers. (4) The low intensity reflector arc.