ABSTRACT
All black-and-white films differ in their sensitivity to different colours. Some films are effectively sensitive to only blue and green light. These are known as orthochromatic films. Some films have more red sensitivity and, being roughly sensitive to all wavelengths of coloured light, are known as panchromatic films. Panchromatic film does not respond equally to all colours in the spectrum. This is in part what gives each type of film a different ‘look’ from another. To produce their effect, coloured filters reduce the energy from some part of the visible spectrum. Some camera light meters do not respond well to filtered light and can give a misleading reading. Bracketing the shot with half a stop and under- or overexposing by one stop around the indicated exposure value may help. For filters that affect the whole image, those that screw into the lens and are made of glass offer the best quality.
