TIME EXPOSURES Exposures sufficiently long to be given by hand, the duration being determined by closing the lens at will, as distinguished from " instan taneous " exposures, or those that must be given automatically by a mechanical contrivance. A time exposure may be of any duration from a quarter or half of a second up to several hours. If very long, the lens cap will form the most con venient method of uncovering and covering the lens, but for exposures up to eight or ten seconds a mechanical shutter is preferable, as when this is employed the photographer can watch moving foliage or any subject that requires care in seizing the opportunity for making the exposure, and, without touching or looking at the camera, can release the shutter at the critical moment, thus ensuring exposure under the best conditions. If foliage should move or any other accidental necessity arise, he can at once close the shutter, if the exposure is nearly completed, and secure a negative that shows absence of movement. In long time exposures it may frequently become necessary to give several short exposures to make up the total time. The photographer should
acquire the art of capping and uncapping the lens without imparting a tremor to the camera.
For timing exposures, there is nothing better than d chronometer or a watch with a seconds hand. One exposure meter is fitted with a chain which swings to and fro in a given time and is approximately correct. Counting is fairly satisfactory if one has learnt to count always at the same speed, but a second is longer than the average worker imagines, and considerable prac tice is necessary before one can count without a watch with safety. A common plan is to count in a normal manner, as follows : " One little second," " two little seconds," " three little seconds," and so on, practising this until each sentence takes one second to repeat. For longer exposures, both for camera and dark-room work, a watch or d special dark-room clock is to be preferred.