The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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parabolic reflector are also required. The majority of beginners will most likely confine themselves to small plates, the lantern sizebeing the most usual. Special forms of light
cameras are now made for this size for use with the eye-piece, and from practical experience the beginner is recommended to always use the eye-piece till he has become more proficient. The camera, however, must have a sufficient pull of bellows, about 12 or 14 inches. For focussing, the usual ground glass is utterly useless, the only method being to use a piece of patent plate which has lines drawn upon one surface with a diamond; and when these lines and the image are both in focus with a compound focusser, the correct focus is obtained. Or another
Fig. 106.
method consists of moving the head from side to side, and when the image moves with the head the object is not in focus; when, however, it remains stationary the focus is correct. The method of attachment of the microscope to the camera differs much, - some employ loosely fitting black velvet sleeves; others employ a brass connection, into which the microscope tube either screws or merely slides. In some cases, especially those in which yellow predominates, isochromatic plates will be found the best. In others, where orange or orange-red is the prevailing colour, then plates specially sensitised for these rays will be found most effectual. If the illuminant used is gas or lamp light, then the exposure may be considerably shortened by always using iso-chromatic plates as these plates are much more sensitive to such