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Dark Slide

plate, slides and double

DARK SLIDE, The English term for the plate holder. It is also termed the single or double back. The double backs are the most convenient, as they carry two plates in but little larger space than required for one. The dark slide, usually made of wood or metal, must be perfectly constructed so as to be absolutely light tight. It should also fit easily in the grooves of the camera made to receive it ; no jarring or sticking mnst take place. In a double dark slide two plates are placed with their sensitive faces outwards. They shonld fit exactly into the places provided for them and held firmly into position by means of catches. A piece of blackened tin or cardboard is placed between them to prevent the light passing through one and affecting the other. On both sides is a sliding shutter, which is either drawn up or right out before the plate is exposed, and returned to its position after exposure.

In some makes of dark slides spring catches are fitted to prevent the slides from being drawn out by accident, and others have the shutter hinged, so that when drawn up they fold back on to the top or side of the camera away from the wind and danger of being broken.

Cameras are usually provided with three double dark slides, but if a changing bag be employed one ocvill be suf ficient. The slides should be plainly numbered to prevent the same plate from receiving two exposures. To obviate this many arrangements have been devised by which the slide, when once drawn out and replaced, cannot be withdrawn a second time until another plate has been placed in.

Dark slides should be fitted with carriers if more than one size of plate is used. These are frames of blackened wood fitting into the space made for the plate, so that plates smaller than the ones the camera is intended for can be used. Carriers are also made for exposing films on negative paper.