What results in white or dark areas on a film?

The presence of white or dark areas on a film is typically a result of overlapping film during processing. When films are processed, they must be placed in the developing solutions and then rinsed properly without touching or overlapping with one another. If one film overlaps another, it may not receive consistent exposure to the chemicals, leading to uneven development. This can create areas that appear lighter or darker because certain sections may have been overdeveloped or underdeveloped.

In contrast, while factors like drying, exposure to light, and incorrect chemical ratios can impact film quality, they do not specifically result in the distinct white or dark areas created by overlapping. For instance, adequate drying primarily prevents water spots or streaks, exposure to light primarily causes fogging of the film rather than these distinct areas, and incorrect chemical ratios can lead to overall poor development but not the specific pattern of white and dark spots that is characteristic of overlapped films.