Bird studies with a camera

by Frank M. Chapman

The reflecting camera now in my possession was designed and made by John Rowley, of the American Museum of Natural History, and was fully described and illustrated by him in Bird-Lore for April, 1900. It resembles the upper half of the twin-lens camera in that a mirror, set at an angle of forty-five degrees to the plate, is interposed between the latter and the lens, and reflects its image to a ground glass on top of the camera. This mirror, however, is movable, and the desired object appearing in focus on the ground glass, a lever is pressed downward which raises the mirror to the top of the box, where it automatically releases a focal-plane shutter (see beyond, under The Shutter) directly in front of the plate, when the image-bearing rays, before intercepted and reflected by the mirror, are registered on the plate, from which the slide had previously been drawn.

When the focal-plane or curtain shutter has been set and the slide drawn from the plate holder, this camera is like a cocked gun, which may be fired the moment it is sighted; or, in other words, the exposure may be made the instant focus is secured. With this camera one may take advantage of any offering opportunity to secure a picture of a bird or beast when afield, and this fact, by increasing the possibilities of an outing, adds greatly to its pleasure.

Mr. Rowley has so designed this camera that it may be used from a tripod as well as in the hands; but when the tripod camera is to be left, perhaps for hours, hidden near some bird’s nest, I prefer to employ the long-focus for this purpose, and retain the reflecting camera for possible use on the birds that so often approach closely when one is in hiding. The advantages possessed by this camera are so apparent that it doubtless will soon be placed on the market.

The Lens.—Professional photographers differ so widely in their opinions of the relative qualities of the various makes of lenses now on the market, that I approach this subject with diffidence, and, without presuming to offer advice, present the results of my experience both as to lenses and the requirements of the bird photographer. In regard to the latter phase of the much-discussed question of “What lens shall I use?” I may speak with more confidence. For nests with eggs or young birds—subjects which may be approached closely—a six- to eight-inch-focus lens forms a large enough image, and at the same time gives depth of focus and sharpness of definition without the use of the smaller diaphragms. In photographing birds, however, it is generally difficult to get within “shooting” distance, and at least a fourteen- to sixteen-inch lens is needed in order to secure an image of sufficient size. Depth of focus is here, in my opinion, not desirable, and the focal point—the bird—is brought out more clearly by the fusion of all the objects back of it into a uniform background.

When a bird, either young or old, is the subject, great speed may be required, and sometimes under light conditions which severely test the qualities of the lens. To fully meet these demands of distance and time two lenses would be needed; but, aside from the increased cost and the inconvenience of using two lenses, the great size and weight of a long-focus lens are drawbacks. These objections are largely overcome by the use of the symmetrical lenses placed in most of the long-focus boxes, or, if expense be not considered, by a “convertible” lens.

For several years I have used a “Victor” lens, sold with the “Premo” long-focus camera. The combined focus of the front and back lenses is seven and a half inches, of either of the lenses alone, fifteen inches. The single lens therefore, the distance being the same, gives an image double the size of that cast by the two lenses together.

This lens has been thoroughly tested, and many of the pictures given in this book were made with it. When the conditions are favorable and the subject not extremely difficult it yields satisfactory results.

The “convertible” lenses of various makers are also separable, and where the rear and front lenses are of different foci three focal lengths are obtainable. These lenses are of the highest grade, and consequently expensive. In a bright light, or where great speed is not required, they do not seem to be as superior to the trade lens as the much higher price would lead one to expect. But in dull days, or in the shadow, or where extremely rapid exposures are necessary, their superior qualities become evident. My experience with these convertible lenses has been limited to the Zeiss Anastigmat, Series VII a, of which I am now using a No. 10 with a combined focus of eight inches, the front and rear lenses both having a focal length of fourteen inches. This combination is preferred to one in which the component lenses are of different foci, because of the greater speed of the two when combined, and furthermore, because, being of the same focus, they could, if occasion arose, be used in a twin-lens box. The speed of the combination is registered at F. 6.3; that of the single lenses at 12.5. With the former the most rapid exposures can be made successfully, while the latter are sufficiently fast to permit of ordinary instantaneous work. This lens is stated to cover a 5 × 8½ plate, and when in use on a 4 × 5 camera gives a high degree of illumination and perfect definition.

The telephoto lens may be employed in certain kinds of bird photography with not unsatisfactory results. Its disadvantages are lack of speed, an exposure of at least one half a second to a second being required at F. 8 in bright sunlight, the necessity of extreme care in focusing, and of absolute rigidity of the camera at the time of making the exposure. In short, the telephotographer needs more time, both before and after pressing his bulb, than the bird photographer is often accorded. However, with such subjects as nests high in trees or on cliffs, Herons and other shore-inhabiting birds, Ducks on the water or Hawks perched in leafless trees, the telephoto will be found serviceable.

Negatives are frequently secured in which the figure of the bird, while small, is sharp, when, by enlargement, a desirable picture can be made of what in the original was too small to be easily distinguishable. An increase in size of two diameters is possible from any fairly sharp negative, but if the object be in perfect focus an increase of four diameters may be made.