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CH. VIII] PREPARATION OF LANTERN SLIDES 213
§ 329. Printing lantern slides by the aid of a camera. — Unless the negatives from which lantern slides are to be made have the part to be shown of exactly the size of a lantern slide, the transparency or positive cannot be printed by contact. Then one can use a photographic camera and print the transparency as follows : The negative is put in a suitable opening or in the proper "kit" or frame in the end of a copying camera (fig. 116-119), and the objective in the second segment. The picture or film side of the negative must face the objective. Then the end of the camera holding the negative is elevated sufficiently to get a sky background through the window ; or the camera is left level and a large piece of cardboard or white blotting paper is set at an angle of about 45 degrees out of a window and the camera pointed toward it. In either case the entire lantern slide will be evenly illuminated and a good print can be obtained.
Now focus the picture of the negative sharply on the ground glass of the camera and get it of the proper size by pulling out or closing up the bellows.
Print the positive by putting a lantern-slide plate in the plate holder in the usual manner and exposing it. Then develop as usual.
It is to be noted that the film surface of the negative and the sensitive surface of the lantern-slide plate face each other by this method exactly as for contact printing (§ 32ga).
§ 330. Camera for lantern slides. — If one is to make many lantern slides it is a great convenience to have available a special
§ 329a. White prints on a black ground. — By using an ordinary negative giving black lines on a white ground one can get white lines or a white picture on a black ground by applying the method just given for printing lantern slides by means of a camera and an objective. Place the negative in position, but with the film side facing away from, not toward the objective as for an ordinary lantern slide. Use a lantern slide or any other kind of plate and make the picture just as for the lantern slide. The glass picture thus produced will be a positive like a lantern slide but it will have all the parts reversed exactly like a negative. If now this picture is used as a negative and printed with cyco, velox, argo, haloid or any other printing paper the picture will appear white on a dark ground.
Of course, any lantern slide can be used for making prints, but the picture will be reversed in every way, the lights and darks, the printing, etc. To prevent the inversion of the printing one can use an objective and camera as described in Ch. X, § 512.