Plate-hold′er.
（Photography.) a. Also known as dark-slide or slide. That part of a photographic camera which is used to contain and transport the sensitized plate. It consists of a thin, flat, rectangular frame or box, square or nearly so, the dimensions of which enable it to take exactly the place of the ground-glass screen upon which the visible picture falls. The back of the plate-holder is provided with a door, which, when opened in the dark room, admits of the introduction or withdrawal of the collodionized plate. The front, that is, the side which faces the lens, has a thin sliding shutter, which serves to uncover the sensitive surface when the slide is in its place, so that it may receive the rays of light, the action of which forms the photographic image, exactly in the position occupied by the ground glass during the operation of focusing. By this contrivance the plate is taken to and from the camera in total darkness. Inside frames or kits are used within the plate-holder for making small negatives. b. A pneumatic device used to hold the plate during development.
