Temperature and humidity are less damaging than light exposure. The most intense of typically used light sources, slide projector illumination is approx. 10 times that of daylight and recommended maximum length of exposure for a slide is 30 seconds. In light fading, the bright highlights go first giving the characteristic washed-out look. The three primary dyes in the color film emulsion layers fade at different rates, thus altering the contrast and the relationships between colors.
Photographic materials are extremely vulnerable to the effects of residual chemicals.
If processing chemicals are not completely removed, the images gradually will deteriorate and eventually will be destroyed. Also, protective storage cabinets create storage environments. Nowadays, many products have improved dark-storage dye stability, notably Kodachrome and Ektachrome slide duplicating film. Fungus growth Fingerprints, dirt and dust can all contain chemicals or fungus spores which might harm a photographic image. Fungus growth on photographs may be seen as a white or colored area which, in advanced stages, might show a filamentary pattern.