Light micrograph of the emulsion from 'Kodachrome 64' colour transparency film. This film works on a subtractive process, a method of colour synthesis whereby two or more superimposed colourants are used to selectively absorb their complementary colours from white light. It has three layers of emulsion (a suspension of light-sensitive silver halide grains in a transparent gel) which respond seperately to blue, green & red light. During the developing process the image recorded by each layer produces clouds of dye of the complimenary colour; yellow, magenta or cyan. Together the three layers can form any colour of the spectrum. Magnification: x200 at 35mm size.