The Eastman paper films for the roll-holder are prepared in continuous bands, and are rolled up on wooden spools and neatly packed in paper boxes.
The spool may be removed from its box and placed in the holder in daylight, at the expense of the outside roll or length of paper necessary to extend from the spool to the winding-reel, so that if one were so situated as to find it necessary to change rolls in the field, the loss would be trifling—being at the utmost not more than would be required for two exposures from each spool.
The proper course, however, is to charge the holder with its spool of film in the dark room before going abroad.
In doing this it is necessary that the light in the room should be strong enough to enable the operator to see comfortably; but of such a quality as not to injure the paper, which is at least 25 per cent. more sensitive than the same emulsion would be if on glass instead of paper.
Figure 1 gives a general idea of the shape of the holder, with the slide partly drawn to show a portion of the film. Also may be seen the brass loops or clamps p182 which hold the cover securely over the working parts, and the key at the bottom which turns the reel to which the loose end of the paper is attached.
FIG. 1.
FIG. 2.
The working parts are fastened to a light metal frame, and consist of a spool of film at the right end, and the winding reel at the left, as seen in Figure 2. Both the spool and the reel are provided with spring brakes, that prevent the uncoiling or unrolling of the paper from either the spool or reel. The milled p183 heads of the chucks which hold the near ends of the spool and reel are provided with pawls, which, while permitting them to turn easily in the right direction, prevent the possibility of turning the other way.