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A material used as a light sensitive coating for a type of plate that is used for digital platemaking. The coating is sensitive to a portion of the electromagnetic spectrum, which allows the plate to be digitally imaged by lasers. The emulsion on a silver halide/diffusion plate is made of photosensitive compounds that are similar to the compounds in photographic film. The earliest type of silver halide plate was made with a polyester base and was not sensitive to visible light wavelengths. It was a colorblind plate. The plate was capable of only single or spot color printing. Early plates with a metal base were also colorblind. Subsequent types of silver halide/silver emulsion metal plates have been created that are sensitive to visible light wavelengths. The plates are panchromatic. They are imaged with various lasers including 488 nm blue lasers, 532 nm FD-YAG lasers, and red lasers at 670 nm. The plates have a high resolution with screen rulings of 300 lpi or more. A silver halide/silver emulsion metal plate is capable of long press runs. Because the coating on the plates contains silver, which is a toxic heavy metal, any portion of the coating removed during processing must be handled as hazardous waste. The plates also tend to be more expensive than other types of plates because of the silver content.
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