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Abstract
The characteristics of Ilford Colour are discussed so far as they affect the problem of duplication. The need for a negative contrast mask is established and its ideal characteristic derived. An electronic method is described capable of producing instantaneously a mask of the requisite nature. This is done by modulating the television-type raster on a cathode ray tube acting as the light source for a contact printer. Requirements of the c.r.t. phospher, optics, photomultiplier, amplifier and scanning, timing and protection circuits are dealt with. Five Appendices provide a detailed mathematical analysis of the inter-relation of the characteristics of the original transparency, negative contrast mask, static and dynamic gain of the amplifier, bandwidth of the mask image and signal/noise ratio.