Abstract: 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.

Abstract: A lamphouse for use with an enlarger head in the production of prints on variable contrast or on conventional photographic material which consists in part of a light source from which light is directed to a fixed apertured plate. There is on one side of the apertured plate remote from the light source a composite filter, one portion of which passes light in one of two mutually exclusive wavebands and the other passes light in the other of the two mutually exclusive wavebands. The composite filter is moveably mounted in relation to the apertured plate so that in one position the light passing the filter is in all of one of the mutually exclusive wavebands and in the second position the light passing the filter is in all of the other of the mutually exclusive wavebands. In intermediate positions of the filter a varying mixture of light of the two wavebands is transmitted.