Part 10 (1/2)

The camera must on no account be moved between the exposures, nor the focus changed. After making the first exposure the correct focus for the second is obtained by moving the subject backward or forward until an exact focus is secured, and not by moving the camera or ground gla.s.s. The whole apparatus should be painted a dead black.

When the attachment is in place it will be noted on the ground gla.s.s that while the strip B is just one-half the size of the opening in A, it does not cut off just one-half of the ground gla.s.s, a line drawn through the center of which shows that a s.p.a.ce in the center of the plate about one-half an inch in width receives a double exposure, but this is not apparent in the finished negative. The figure should be posed as near the center of the plate as possible in each instance.

This apparatus, as described, is only available for making two figures. By making B narrower, or one-third of the width of the opening in A, three figures may be made, using each time a separate piece to cover up that portion of the plate exposed, and by changing the form of B to that shown in Fig. 95, four positions can be secured.

[Ill.u.s.tration: FIG. 95.]

Val Starnes describes[8] another and still simpler method. He says: Take a light card, mount and carefully cut from it a disc that will fit snugly inside the rim of the hood of your lens, resting against the circular interior shoulder (Fig. 96). Cut from this, in a straight, true line, a small segment (Fig. 97). The exact amount to cut off you can determine by slowly thrusting with one hand a card with a straight edge across the lens hood, looking the while at the ground gla.s.s; when the shadow has crept _almost_ to the center of the focusing screen, hold the card firmly in place and notice how much of the circle of the hood is covered by it: cut from your disc a segment corresponding to the amount _left uncovered_. Don't let the shadow creep _quite_ to the center of the ground gla.s.s, for you might go the least bit beyond, and an unexposed strip would result. Now paint your disc a dull black; loosen the hood of your lens on its threads, so that it will revolve easily and freely, and you are ready for business.

[8] ”American Annual for 1895.”

[Ill.u.s.tration: FIG. 96.]

[Ill.u.s.tration: FIG. 97.]

Get your focus and then place disc in hood of lens, straight edge perpendicular (Fig. 98). Cover lens with cap or shutter; insert plate-holder and draw slide; pose your figure _directly in front of uncovered portion of lens_; expose. Next, without touching disc, slide, or anything but the hood, gently revolve the hood on its threads one-half turn (Fig. 99), and pose your figure on opposite side; expose. The trick's accomplished.

[Ill.u.s.tration: FIG. 98.]

[Ill.u.s.tration: FIG. 99.]

Another arrangement devised by Mr. Frank A. Gilmore, of Auburn, R. I., is shown in Fig. 100.

A black-lined box is fitted to the front of a camera. The front of the box is closed by two doors. On opening one door a picture may be taken on one side of the plate; on closing this door and opening the other, the other half of the plate is ready for exposure.

[Ill.u.s.tration: FIG. 100.--CAMERA FITTED WITH ARRANGEMENT FOR DUPLEX PHOTOGRAPHY.]

The subject poses in one position and is photographed with one door open, care being taken to bring the figure within the proper area of the negative. The finder enables this detail to be attended to. Then the door is closed, the other is opened and the second exposure for the other half of the plate is made with the subject in the other position. It is not necessary to touch the plate-holder between the exposures. The cover is withdrawn, the one door is opened and the shutter is sprung. The doors are then changed and the shutter is sprung a second time. Time exposures are rather risky, as involving danger of shaking. A picture made by Mr. Gilmore will be found on the next page.

[Ill.u.s.tration: By F. A. Gilmore. From _Scientific American_. FIG.

101.--SPARRING WITH HIMSELF]

DOUBLE EXPOSURES.

[Ill.u.s.tration: By C. A. Bates. FIG. 102.--RESULTS OF A DOUBLE EXPOSURE.]

[Ill.u.s.tration: Copyright, 1894, by W. J. Demorest. FIG. 103.--RESULT OF A DOUBLE EXPOSURE.]

Amateurs often obtain unexpected results from carelessness in exposing their plates. Some very amusing pictures can, however, be obtained by making two different exposures on one plate. The subject should, of course, be of a very different nature. Our ill.u.s.trations, Figs. 102-3, are examples. In making these it is necessary to give a very short exposure in each case, about one-half the amount that would be ordinarily required. The negative must be carefully developed, using plenty of restrainer. Similar effects can, of course, be obtained by printing from two different negatives, but the results are, as a rule, inferior.