The rapid dry plate and the quick acting lens have created a necessity for a shutter that would make an instantaneous exposure, in order that sharp pictures might be made of objects in motion.
This has been accomplished in a variety of forms, the earliest and simplest of which is The Drop Shutter
The Drop Shutter, which consists of two pieces of wood, each having a hole cut into it, and so arranged that when one piece is placed upon the end or hood of the lens (which fits into the circular opening), the other piece can be made to slide up and down against it, thus for an instant bringing the two openings opposite, and making the exposure depend upon the rapidity with which one opening passes the other.
Fig. 1 represents the common form, in which the release is made by the withdrawal of a metal catch, which fits the indent in the side of the sliding upright piece. Fig. 2 represents an improved form, in which the release is made by pressing a rubber bulb connected with a rubber tube attached to a metal valve.
The action of both these styles of drop shutter may be hastened by using rubber bands to quicken the fall of the sliding piece, as represented in Fig. 2 by A and B. So that while a rapid exposure might be made by the fall of the slide, by its own weight, it would not be quick enough for an object moving across the plane of focus, but might be sufficient for an object moving away from or toward the lens. By the use of the rubber bands the exposure may be made as quick as a flash, or the small fraction of a second, thus enabling one to secure a sharp impression of the trotting horse, the railroad train, the racing yacht, and many other interesting and difficult subjects.
Another peculiarly effective form of shutter is that known as which is a small and compact instrument, made of metal and rubber, by which an exposure of 1/200 part of a second may be made, with the power of reducing the speed to about one-half second.
The Prosch Eclipse Shutter.
A late and decided improvement on the Eclipse Shutter has been produced by Mr. Prosch, which he has named the "Duplex."
Prosch's Duplex Shutter is intended both for "timed " and instantaneous exposures.
It is equal to any requirement for the most rapid work, and as a time shutter, exposures can be made of from one-half second to any duration required.
The peculiarity of this shutter is that the exposing slides are placed between the front and back combinations of the lens, necessitating a separation of the tube at the centre.
Mr. Prosch makes a special tube to which is affixed the apparatus of the shutter. This special tube is of the exact size of that to which the lenses belong, from which the lenses are taken and fitted to the special tube. The other is kept for future use if necessary.
All this apparatus is, with the exception of the tripod, enclosed in a neat carrying case, with a telescopic cover, and is carried with a hand-strap. The box contains separate places for from one to six double holders, as may be desired. And there is room for the head-cloth, and an extra box of plates if necessary.
The head-cloth furnished with this apparatus is a light rubber-covered muslin, about a yard or a yard and a quarter square, and its principal use is to cover the head and exclude light from the ground-glass while adjusting the focus. It may also be used to cover the apparatus if caught out in a shower, or to wrap the carrying case in under the same circumstances.