Push processing
Encyclopedia
Push processing in photography
, sometimes called uprating, refers to a film developing
technique that increases the effective sensitivity
of the film being processed. Push processing involves developing the film for more time, possibly in combination with a higher temperature, than the manufacturer's recommendations. This technique results in effective over-development of the film, compensating for under-exposure in the camera.
Push processing allows relatively insensitive films to be used under lighting conditions that would ordinarily be too low for adequate exposure at the required shutter speed
and aperture
combination. This technique alters the visual characteristics of the film, such as higher contrast, increased grain
and lower resolution. Saturated and distorted colours are often visible on film that has been push processed.
Pull processing involves over-exposure and under-development, effectively decreasing the sensitivity of the processed film. It is achieved by developing the film for a shorter time, and possibly at a lower temperature. Film that has been pull processed will display the opposite change in visual characteristics. This may be deliberately exploited for artistic effect.
When a film's effective sensitivity has been varied, the resulting sensitivity is called the exposure index; the film's speed
remains at the manufacturer's indication. For example, an ISO
200/24 film could be push processed to EI 400/27 or pull processed to EI 100/21.
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
, sometimes called uprating, refers to a film developing
Photographic processing
Photographic processing is the chemical means by which photographic film and paper is treated after photographic exposure to produce a negative or positive image...
technique that increases the effective sensitivity
Film speed
Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system....
of the film being processed. Push processing involves developing the film for more time, possibly in combination with a higher temperature, than the manufacturer's recommendations. This technique results in effective over-development of the film, compensating for under-exposure in the camera.
Push processing allows relatively insensitive films to be used under lighting conditions that would ordinarily be too low for adequate exposure at the required shutter speed
Shutter speed
In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open....
and aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
combination. This technique alters the visual characteristics of the film, such as higher contrast, increased grain
Film grain
Film grain or granularity is the random optical texture of processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons. While film grain is a function of such particles it is not the same...
and lower resolution. Saturated and distorted colours are often visible on film that has been push processed.
Pull processing involves over-exposure and under-development, effectively decreasing the sensitivity of the processed film. It is achieved by developing the film for a shorter time, and possibly at a lower temperature. Film that has been pull processed will display the opposite change in visual characteristics. This may be deliberately exploited for artistic effect.
When a film's effective sensitivity has been varied, the resulting sensitivity is called the exposure index; the film's speed
Film speed
Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system....
remains at the manufacturer's indication. For example, an ISO
Film speed
Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system....
200/24 film could be push processed to EI 400/27 or pull processed to EI 100/21.
External links
- Push processing and pull processing at Ilford PhotoIlford PhotoIlford Photo is a manufacturer of photographic materials known worldwide for its black-and-white film and papers and chemicals, as well as its range of Ilfochrome and Ilfocolor colour printing materials. Ilfochrome was formerly called Cibachrome, developed in partnership with the Swiss company...
- Push/Pull Processing at Kodak