Illuminating system for producing prints on variable contrast photosensitive material, filter strip for said system and lamphouse comprising the same

摘要

An elongated two-color light-transmitting filter strip of a light-transmitting material has a first zone of its length which transmits light in a first of two mutually exclusive wavebands, a last zone which transmits light in the second of two mutually exclusive wavebands, and a middle zone of the strip having discrete elements which transmit light in the first of the two mutually exclusive wavebands and discrete elements which transmit light in the second of the two mutually exclusive wavebands, the elements having equal areas and being so arranged that there is a progressive change in the transmission of light in the two mutually exclusive wavebands along the middle part of the strip and being so arranged that there is no single line of demarcation dividing that part of the filter which transmits light only in the first of the two mutually exclusive wavebands from that part of the filter which transmits light only in the second of the two mutually exclusive wavebands. An illuminating system comprising this filter strip and a lamphouse in which the illuminating system and filter strip can be used are likewise described.