Color photographs begin as black and white negatives. Color film consists of three layers of emulsion, each layer basically the same as in black and white film, but sensitive only to one third of the spectrum (reds, greens or blues). Thus, when colored light exposes this film, the result is a multilayered black and white negativeAfter the negative images are developed, the undeveloped emulsion remaining provides positive images by "reversal." The remaining emulsion is exposed (chemically or with light) and the film developed a second time with a different developer. As it converts the light-sensitive silver compounds to metallic silver, the developer becomes oxidized and combines with "coupler" compounds to produce dyes.The three dyes formed, one in each emulsion layer, are the subtractive primaries yellow, magenta and cyan. All silver is then bleached out and each layer is left with a positive color image.Thus reds in the subject produce a heavy silver deposit in the red-sensitive layer in the negative, but no trace on the other layers.Then after reversal, only yellow and magenta remain which together make red. As shown in the illustration, the cyan is all but gone.After the film is processed and the silver is removed, what remains is called a "Dye Cloud" and as shown in the "enlarged" illustration below the clouds interaction creates a red color.SUBTRACTIVE COLOR SYNTHESIS uses paints, dyes, inks, and natural colorants to create color by absorbing some wavelengths of light and reflecting or transmitting others. This subtractive action is the basis of photographic filters, almost all films and color papers, and photomechanical reproduction in color.White light is composed of all visible wavelengths, which can be divided into three primary-color bands, red, green and blue. A colorant that absorbs one wavelength band has the combined color of the other two; it is the complement of the color it subtracts from white light. Thus:Primary P...
