The method of using the telephoto attachment is very simple, but requires very great care, particularly in the matter of focussing. Suppose that an exposure has been made in the ordinary way upon a certain object; the lens is then removed from the camera front and screwed into the tube of the telephoto attachment, forming a small telescope; the whole combination is then put back on the camera as if it were the ordinary lens. Upon the ground glass or focussing screen will be seen an enlarged image which may be made sharp or distinct by adjusting the focus by means of the rack and pinion movement on the telephoto tube, just as a field glass is adjusted to suit the eyes of the observer. If greater amplification be desired it is obtained by moving the front of the camera, holding the lenses farther from the ground-glass and then readjusting the focus as before. It will be seen from this that the attachment forms a lens of variable focus, changeable at the pleasure of the operator within the limits of the camera.
Roof and Dome, Milan Cathedral—Telephoto Lens, from Same Corner of Piazza.
Some of the attachments on the market require a camera with a very long bellows, because the difference between the foci of the negative and positive lenses is not great enough to give ample power unless the combination is several feet from the plate. With my own attachment, eight inches from the plate the image is equal to that formed by an ordinary lens of twenty-four inches focus; while at twenty-four inches from the plate it is equivalent to that of a lens of sixty-four inches focus.
The camera used in making the accompanying illustrations takes a plate measuring four by five inches, and the bed allows an extension of twenty-four; and when closed for transportation the box measures seven by seven by six-and-a-half inches.
Of all my experiences in photography none were so unsatisfactory as my attempts on mountain scenery with an ordinary lens. This was especially true of the photographs of the Alps made while tramping through that heavenly tramping ground, Switzerland. The small camera made the mountains look like little humps of rocks and snow, and all the views made from a great elevation seemed to be like photographs of the waves of the ocean, smoothed out flat. These results caused me to experiment in the direction of telescopic work with the camera.
It is often the case that grand mountains appear at their best only from some point so distant that the ordinary lens can produce little or nothing of the desired effect.
One of the most charming views in Switzerland is the evening view of the Jungfrau as seen from the Höheweg or promenade at Interlaken, about sixteen miles from the mountain. With her robes of dazzling white she rises majestically above the Lauterbrunnen Thal to a height of nearly fourteen thousand feet. Upon several former occasions I had endeavored to photograph this queen of the Bernese Oberland, but did not succeed until I used the telephoto attachment. The two illustrations of this view [pp. [462]-[63]] were made from the same standpoint on the Hoheweg, one with the ordinary lens, the other with the telephoto attachment added to the lens, no change being made in the camera at all. It is a pleasure to note the wonderful detail in the telephotograph, and not only that, the mountain seems to rise, giving the impression of abruptness which rarely if ever is obtained with an ordinary lens. I suppose something of this result might have been obtained with the ordinary lens had I been up in a balloon at an elevation of about four thousand feet and about three miles from the Jungfrau. The pictures of this mountain taken from the Wengern Alp do not give this beautiful effect.