Push printing
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Pushprinting_4_stops.jpg
Top: without changes. Bottom: pushed four stops.
In photography, push printing and push developing refer to a process where a picture is printed as if it were a film speed higher than intended by the film manufacturer. For instance, a photo which is metered one f-stop under can be pushed a stop to compensate either in developing or in printing.
In push developing(also known as push processing), the developer changes the development time or temperature to increase contrast. By leaving the film in the developer longer the highlights increase in silver density. When doing this, the entire roll must be pushed; pushing a roll during developing gives better results than pushing it in printing, but the entire roll must be metered "off" the same amount. That is, if one picture is -1; they must all be -1. Push developing a film can not be undone.
Photos may also be pushed in printing. The paper is exposed more (through aperture or time) but the development time stays the same; as a result, the photo is lightened so that more detail is visible. This process affects the print and not the negative and so can be tried to different degrees. Side effects may be that colors are weakened, contrast may be over-emphasized, and considerable grain may be added to the image. Push printing is not suitable for all types of film.
Push printing is sometimes done without the photographer's knowledge or permission, especially on newer automated systems which prompt the developer about potential "problem" photos. In the example to the right, one picture on an ISO 400 roll was pushed four stops.
The image shows two photos of a woman in a car: the top one was metered according to the average light within the full image frame. As a result of the bright light in the background, her face was left in silhouette. The developer pushed the photo four stops to compensate, bringing out the features of the subject's face. In this case, the photographer returned with the film to have it reprinted the way he intended.
See also: pull printing