The colours recorded in an image have a number of possible sources. The first and most obvious is the inherent colour of the subject, although tones will vary as the amount of light reflected from its surface changes. The quantity of light returned to the camera is dependent upon the nature and angle of the reflecting surface. A face becomes darker and cooler in tone as its surface curves away from the light, the angle of incidence increases and less light is returned. The second source of colour is that of the illuminating light. The colour and quality of daylight change as we have already seen, and so alter the colours recorded in an image. Also bear in mind that when reflected, light acquires the colour of the reflecting surface. Hence the predominant colours surrounding a subject may well influence the whole image. Colour is particularly critical in portraiture because people are able to judge flesh tones very accurately. Be warned that colour casts will be noticed very quickly.
Choice of film is also significant since no two emulsions behave in the same manner. Some have a warm reddish bias while others produce cooler images with stronger blues and greens. However, modern films are so good that the issue reduces to one of personal preference. The best advice is to try a range of films and stick with the favoured few. This encourages an understanding of the emulsions, which is probably more important than the choice of manufacturer.Two other sources of colour are filters and printing processes.
Filters can be used to bring about all sorts of colour shifts, subtle and not so subtle, but if true-colour images are the ultimate goal the more exotic varieties have little to offer. In the processing lab or darkroom a final battle must be fought to produce what the photographer requires. Perfect colour matches are difficult to achieve even with well regulated processes. A good lab produces reasonably consistent, high-quality results but small variations still occur and can be detected by direct comparison or an experienced eye.