HAND CAMERA (Fr., Chambre a main, Chambre detective ; Ger., Handhamera, D etectiv hamer a, Geheimhamera.) A camera sufficiently light and portable to be used in the hand, instead of on a stand. A collapsible pocket camera having a cloth body was suggested by Edwards as early as 1855. In 186o and 1861 hand cameras of fixed focus with bodies of wood or metal were constructed by Bertsch and by Ottewill, and in the latter year magazine changing-boxes were in use. Enjal bert in 1887 used a leather changing-bag attached to the camera, with a lever for lifting the plates as exposed. The first approximation, however, to the convenience of the modem hand camera appears to be due to Thomas Bolas, who in 1881 described several forms of what he termed " detective cameras," with twin lenses, a focus ing arrangement, and a pneumatic release for the shutter. A reflecting prism was placed in front of the lens so that it might be pointed at a right angle to the direction of the object to be photographed, and thus worked without exciting suspicion.
The simplest pattern of hand camera is the box form, which is usually of fixed focus, the lens being incapable of movement and so adjusted that all objects beyond about seven yards distant will be rendered sufficiently sharp. A typical box form camera for films A has two finders x and r, for sighting the object, for plates being shown at B. In this model, focusing is effected by turning a milled screw o; a hinged door at the front allows access to the lens and shutter, and permits the storage of the pneumatic ball and tubing in the recess.
A trigger release is worked by a push at the side ; p is the lever actuating the plate-changing mechanism, and Q, pivoted to the door, acts as a dust excluder.
The details of the plate-changing mechanism differ considerably: C illustrates one effective arrangement, introduced by McKellen. The metal sheaths s containing the plates have pro jecting pins r at their bottom corners, which rest on grooved guide plates u at the sides of the camera. At the end of each groove is a circular hollow, in which turns a revolving disc v, the two discs being mounted on the same shaft. Each disc has a notch in it capable of receiving the pins of the sheaths. The sheaths are pressed forward by the spring w, when the one for vertical and one for horizontal pictures.
The inner case is shown partly withdrawn, isit being the key by which the film is wound. Box-form hand cameras are also made to hold a magazine of plates in sheaths or for use with ordinary dark - slides. Besides the fixed - focus type, they are obtainable with a focusing arrangement working by scale, one of this kind front one bears at the top against a stop-rail x and is supported at the bottom by its pins engaging in the notched wheels. To change a plate, the wheels are turned simultaneously by means of a handle outside the camera, thus carrying down the front sheath, the pins of which remain caught in the notches until the top clears the stop-rail x. The sheath now falls into the bottom of the camera, and the handle is turned in the reverse direction until the wheels engage with the pins .of the second sheath, which is then in position for exposure.
A representative example of a folding hand has been made winding is continued until all the black paper has been wound off the original spool, when the camera back may be opened and the exposed spool withdrawn.
A folding camera for plates is illustrated at camera for films is shown at D. The principal movements and fittings are : j, key for winding film ; s, focusing screw ; T„ rising-front pinion ; M, finder ; N, spirit level ; o, lens with dia phragm shutter ; P, cross-front movement ; Q, bush for tripod screw, for attaching the camera to a stand if required ; R, focusing scale.
The winding mechanism for films usually varies little from the system shown at E. Having removed the sliding back, a charged spool of film s is placed in a recess at one side of the camera and fits on two small pegs. An empty spool T fits a recess at the opposite side, and is turned by the winding screw u which engages in one of its ends. Having inserted both spools, the end of the black paper on the full one is drawn out until it can be pushed through the slot seen on the empty spool, and the key is given a single turn. The back is then replaced P. A more substantial and elaborate example of what is known as the " hand or stand " type is shown at G ; this can be employed for nearly all descriptions of work, being either held in the hand or supported by a stand.