This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Exposing Or Printing When Making Slides By Reduction. The method of printing lantern-slides by contact, as previously described, has a limitation. The largest possible picture on a lantern-plate cannot well exceed three inches in width or height; it would only show a little more than half of the picture from a 4 x 5 negative, while, with negatives of any larger size, so little of the subject would appear on the slide that this method for all but a few exceptional cases is impracticable. Therefore, all such slides must be made by "reduction," as it is called. It takes a little longer, and is a little more trouble, but the resulting slides, even when the size of the picture on the negative does not necessitate it, are equally as good, and often better than if they were made by contact.
"LULLABY" Study No. 15-See Page 358 Louis Fleckenstein.
892. The other method has been previously referred to as "printing." This may be called "photographing."
893. Having prepared the apparatus according to the instructions previously given, take the printing-frame containing the negative and place it in the standard at the end of the board. Arrange it facing the window, with the film side of negative towards the camera, the camera being placed at the other end of the board. Observe the image on the ground-glass and secure a sharp focus, and with a rule measure the size of the image. If it is too large, draw the camera back from the negative and proceed to focus again; if too small, push the camera towards the negative. Do this until the desired size suitable for the lantern-slide is secured. It is very essential that a sharp focus be secured, for when the slide is projected on a screen, and, therefore, magnified many times, unless it is sharp it will appear very blurry. If any difficulty is experienced in focusing, it is well to use a magnifying-glass, as this will magnify the image on the ground-glass and assist in obtaining a sharper focus. After focusing, we would advise a smaller stop than for ordinary purposes. This will help to secure absolute sharpness.
894. In order that no white light be admitted between the negative and camera, extend two thin slats or strips of wood from the printing-frame containing the negative to the top of the camera. Over these strips throw a focusing-cloth or any black cloth, to form a hood. This will exclude all light except that coming through the negative.
895. It is advisable always to focus the image as sharp as possible without the use of a stop. If it is necessary to use an extremely small stop, there is danger of a loss of crispness. It is also a good plan to stick a lantern-slide mask on the center of the ground-glass in the camera, and use this for the guide in obtaining the exact size of the view desired. By excluding all light from the lens, except that which comes through the negative, the slides will be bright and clean.
896. Another very convenient way to make slides by reduction, is to have two view cameras, one larger than the other. Remove the front board from the larger camera, place the ground-glass end towards the light, and then place the smaller camera in front of the larger one, with the lens pointing through what was formerly the front of the large camera. In other words, place the lens of the smaller camera through the opening from which the lens of the larger camera has been removed. By throwing a dark cloth over the two cameras all light is excluded. Take an old double plate-holder, cut out the division and withdraw both slides. Place your negative in the holder in exactly the same manner as though an exposure were to be made, the film side towards the front of the camera. The ground-glass will then come between the negative and the light, acting as a diffusing screen, and the diffused light will evenly illuminate the negative. With the second camera make the copy.