Enlarger

An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives, or from transparencies.

All enlargers consist of a light source, normally an incandescent light bulb, a condenser or translucent screen to provide even illumination, a holder for the negative or transparency, and a specialized lens for projection. The light passes through a film holder, which holds the exposed and developed photographic negative or transparency.

Prints made with an enlarger are called enlargements. Typically, enlargers are used in a darkroom, an enclosed space from which extraneous light may be excluded; some commercial enlargers have an integral dark box so that they can be used in a light-filled room.

A condenser enlarger consists of a light source, a condensing lens, a holder for the negative and a projecting lens. The condenser provides even illumination to the negative beneath it.

A diffuser enlarger's light source is diffused by translucent glass or plastic, providing even illumination for the film.

Condenser enlargers produce higher contrast than diffusers because light is scattered from its path by the negative's image silver; this is called the Callier Effect. The condenser's increased contrast emphasises any negative defects, such as dirt and scratches, and image grain.

Diffuser enlargers produce an image of the same contrast as a contact print from the negative.

Dedicated color enlargers typically contain an adjustable filter mechanism - the color head - between the light source and the negative, enabling the user to adjust the amount of red, green and blue light reaching the negative to control color balance. Other models have a drawer where cut filters can be inserted into the light path, synthesize colour by additive mixing of light from colored lamps with adjustable intensity or duty cycle, or expose the receiving medium sequentially using red, green and blue light. These enlargers can also be used with variable-contrast monochrome papers.

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