Bird studies with a camera

by Frank M. Chapman

The “Unicum” shutter is lighter, responds quickly, has a lever to which a thread may be attached for making exposures from a distance, can be easily diaphragmed from the rear, but is not wholly noiseless. There are also other shutters, each possessing good points of its own, and the selection of any one of them for use in medium rapid, slow, or time work can be left to the photographer, who should, however, remember that the time scales on these shutters represent degrees of difference and not exact measurements of time, and that there is great variation in the exposures of different shutters of the same make when similarly adjusted. Thus the “one fifth of a second” of one shutter may be equivalent to the “one second” of another. The scale on most of these shutters calls for a speed not exceeding a ¹⁄₁₀₀ part of a second, but this is far too slow an exposure to successfully photograph a flying bird at short range where a speed of at least ¹⁄₅₀₀ of a second is required.

For very rapid work the choice is limited to one kind of shutter—that is, the focal-plane, which in effect is a curtain with an adjustable slit which is placed directly in front of the plate. Great speed with this shutter is in part secured by increasing the tension of the spring, which acts as its motive power, but more particularly by decreasing the width of the slit. Assuming, therefore, that it takes one second for the slit to pass from top to bottom of a plate four inches high, and that the slit is one inch in width, it follows that each portion of the plate is exposed to the light for a quarter of a second. Decreasing the width of the slit one half, proportionally reduces the time of the exposure, and by this means, in connection with an increase in the speed with which the curtain is moved, an exposure of ¹⁄₁₀₀₀ of a second is possible.

In addition to possessing the advantage of great speed, this shutter also passes a higher percentage of light than a lens shutter even when the actual time of the so-called exposure is the same. This is due to the fact that the lens opening is in no way affected, it being the same throughout the exposure. With a lens shutter, on the contrary, the full value of the opening is given for only a fractional part of the exposure, the parts of the shutter more or less filling the opening during the rest of the time. With a focal-plane shutter, therefore, one may do rapid work under conditions where a lens shutter could not be successfully employed; time exposures, however, can not be made with the focal-plane shutter, and for all-around work the camera should be fitted with both a lens and a focal-plane shutter.

The reflecting camera, as before stated, is fitted with a focal-plane shutter, and, as described, it is released by pressing the lever, which raises the mirror. Lens shutters, however, are released by a pneumatic bulb, or in some cases by a thread or string. When the exposure is to be made from a distance as much as one hundred feet of tubing may be employed. With any length of over twenty-five feet an extra large bulb is required. The ordinary tubing sold by photographers will not be found so well adapted to long-distance work as a less elastic kind, which does not so readily yield to pressure and transmits a larger portion of the force applied when squeezing the bulb.

The Tripod.—A stout two-length tripod is to be preferred to one of the slender multifolding type, in which stability is sacrificed to weight and size. The legs, except the inner sides of the upper section into which the lower section slides, and brass work should be painted bark color in order to make them as inconspicuous as possible. For use in the water a metal tripod will prove more serviceable than one of wood.

A very useful substitute for a tripod is the “Graphic” ball-and-socket clamp designed more especially for bicycle camerists. With it a camera can easily be attached to the limb of a tree, rung of a ladder, or, by screwing a block on to the head of the tripod, it may be employed in connection with the tripod—in fact its applicability will be evident to every one using it.

Plates.—Among the many excellent brands of plates now offered to photographers there is really very little difference. However, it is advisable to select the one you think the most rapid and use it to the exclusion of all others. Under certain circumstances—in photographing Robins, for instance—isochromatic plates will be found desirable, and where a strong head light can not be avoided nonhalation plates may be employed.

So much industry, skill, and patience are generally required of the bird photographer before he makes an exposure that he should guard against all chances of failure from the photographic side. It is therefore advisable to thoroughly test plates which it is probable may be exposed on a very difficult subject. Under no circumstances should the plate holders be needlessly exposed to the light, and when the camera is to be left for an indefinite period with the slide drawn from the holder and plate ready to expose, it should be carefully wrapped in the dark-cloth.

Blinds.—As the sportsman constructs blinds in which he may conceal himself from his prey, so the bird photographer may employ various means of hiding from his subjects. The Keartons recommend an artificial tree trunk for use in wooded places and an artificial rubbish heap for open fields. The former may be made of light duck, painted to resemble bark, and placed over a frame.

The frame of the Keartons’ is of bamboo, but I find white pine answers very well, the main things to be considered being lightness and portability. The frame should therefore be collapsible in order that it may be easily packed.