Camera extract

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The camera extension describes the distance between the film plane and the lens plane in a camera . In the case of so-called view cameras , which connect both levels with a bellows , the camera extension must be measured directly, as long as it is not a telephoto lens that is shorter than its focal length (some wide angles are longer than their focal length).

Extract and extension (compared to the - shortest - setting for infinity) are z. B. needed to determine the image scale and depth of field .

This is not possible with cameras with lenses that have a rotary screw for the extension, because part of the extension takes place inside the lens. For such lenses with an adjusting worm, a scale is required that relates the focus to the aperture in order to determine the depth of field.