ROLL HOLDER OR ROLLER SLIDE.—An arrangement for holding a continuous band of paper or other flexible substance, coated with a sensitive emulsion, in the camera during expo sure. The first roller slide was introduced by Mr. A. Melhuish, about the year 1861, and was used for making paper negatives.
In the usual roller slide the film is unwound from one spool in equal lengths corres ponding to the size of the plate for which the holder is designed, and after it has received the exposure it is again wound on to another roller termed the clamping reel. In this man ner a large number of exposures can be made upon a long band of paper or film, and this is then cut up, and each picture developed.
It is exceedingly compact and very light. When a perfect flexible film has been dis covered, the advantage over glass plates will be incalculable.
The best form of roller slide is that known as the Eastman-Walker roll-holder. It is con• structed in three parts, a body consisting of four side, together with the top and bottom. These latter are held to the body and together by two simple springs which pass down the ends, and by a mere pressure of the finger the roll-holder can be taken apart instantly, and its contents got at in all directions. In
side the body are fitted four rollers, two being small and permanent, and merely form runners for the film to pass over in its passage between the spool-holders. The other two are large rollers, fitted to attachments screwed into the sides of the frame. They are easily remov able, and one fits on to an attachment provided with a brake, which serves as an automatic tension, keeping the film stretched flat and smooth, and prevents it being too freely unwound. There is also an audible and visi ble indicator, enabling the operator to be perfectly as sured, both by sight and sound, that each exposure has been correctly wound off, and a new length placed in position ready for the next exposure. The film is also marked with an automatic perforator, so that no error can be made in cutting up the paper previous to development.
This roll-holder, although occupying the space of three double dark slides, contains suf ficient material to make 50 or more exposures.
It can be easily adjusted to any ordinary camera, care being taken that the position of the film coincides with the plane of the focusing screen.