_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.