A film process designed to produce a positive instead of a negative image after development.
The latent image is developed to a silver image by primary development, then destroyed by a chemical bleach, and the remaining sensitive emulsion exposed by a flash exposure or darkened by chemical treatment. The film then enters a second developing bath before fixing and washing. Emulsions designed for reversal processing are characterized by fineness of grain, but their exposure latitude tends to be lower than normal.
Additionally, in the case of colour, there is film material for making a negative directly from a negative (Colour Reversal Intermediate: CRI — for both 16mm and 35mm stocks). Negative to negative reversal is not normally practised in the industry for black and white. In fact, black and white reversal materials are generally used only in 16mm.