These enlargements may be made with an enlarging camera or with the aid of a Nehring enlarging lens, which is placed between the front and back lenses of the view lens, when, with the ordinary long-focus camera, a magnification of about four diameters may be obtained, the image being thrown on to a piece of bromide paper in the plate holder.
Through enlargement many apparently worthless negatives become of value, and in some instances pictures can be made from different parts of the same negative. From the sportsman-photographer’s standpoint there is, however, one objection to the use of a magnifying lens. It gives deceptive results, and those who are not familiar with its powers are apt to accord the photographer undue praise for his apparent skill in successfully approaching some bird or beast which may have been far out of range. A not wholly unrelated kind of enlargement is sometimes applied to the contents of creels and game bags!
But the animal photographer is so heavily handicapped that in this case the end assuredly justifies the means. As a matter of information, however, it seems eminently desirable to accompany all enlarged pictures by a statement of the extent of their magnification, and throughout this book this plan is followed. Consequently, when there is no mention of enlargement, it may be accepted as a fact that the print from which the reproduction was made was obtained from the negative by contact.
In illustration of these suggestions in regard to the proper lenses for bird photography, a series of pictures is presented which shows the results to be obtained under the same conditions with different lenses.
2. Lens Test No. 1. Mounted Flicker on fence post, distance fifty feet. Eight-inch focus, Zeiss Convertible, No. 10, Series VII a lens; diaphragm F. 8, ¹⁄₂₅ second; Cramer “Crown” plate. Photographed at noon, in sunlight, November 30, 1899.
3. The bird in Test No. 1 enlarged about three diameters.
Placing a mounted Flicker (Colaptes auratus) on a fence post, and setting up my tripod at a measured distance of fifty feet, a series of test exposures was made, of which three are presented as follows: First,2 eight-inch lens (Zeiss Convertible Series VII a, No. 10), stop F. 8, time ¹⁄₂₅ second; second,4 fourteen-inch front lens of the combination, stop F. 16 (equivalent to F. 4 of the eight-inch); third,6 telephoto attachment with eight-inch lens, twenty-one-inch bellows, stop F. 8 of the eight-inch, time one second. Commenting on the results of these tests it may first be mentioned that in the “Unicum” shutter employed exposures of a so-called “¹⁄₁₀₀” and “¹⁄₂₅” seconds gave exactly the same results both with the combined eight-inch lens and the front fourteen-inch lens; the actual time, however, was doubtless not far from ¹⁄₂₅ of a second. The negatives, therefore, show, in the first place, that the long-focus lens is capable of doing fairly rapid work. Continuing our comparison, we observe that the eight-inch gives a fairly wide field, excellent depth of focus, but a very small image of the bird, for which alone the picture has been made. With the fourteen-inch we decrease the extent of the field nearly one half and almost double the size of the object pictured. This, however, has been done at the loss of depth of focus, not even the first of the line of posts running directly into the background being sharply defined, while with the eight-inch all are in focus.
