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.
Extension Device. In order to supply sufficient distance between the ground-glass and the lens, the lack of bellows capacity can be overcome by having a box made of very light material, open at each end. This box can be made either to fit into the place of the front-board containing the lens, or it may be fitted to the rear of the camera in the place of the ground-glass. The latter is preferable where the hand camera is employed, for the reason that the majority of hand cameras are supplied with a very small front-board, permitting of a very short cone only, while, when the cone is fitted to the rear of the camera there will be no obstruction between the lens and the ground-glass, and there is more latitude for adjustment of the size of the copy.
534. When the cone is fitted to the front of the camera it must be arranged so that one end will slip into the space occupied by the front-board and lens, and the other end must be arranged to receive the front-board containing the lens; but, as said before, the attaching of a cone to the rear of the camera is preferable, as a larger cone can be used.
535. When a view camera is employed, the cone should be attached to the front of the camera, as the space for the front-board is much larger, permitting of the use of a larger cone, and the attachment is the same as with the professional portrait camera. (See Illustration No. 2, page 157.) The cone should be made of light wood, fitted closely to the camera, and, in the case of a hand camera, attached to the rear of the camera in the place where the ground-glass frame is fixed. The ground-glass frame or reversible back (provided the camera is fitted with one) must be moved to the other end of the cone, an arrangement being made to attach this part to the cone exactly the same as it was attached to the camera.
536. The size of the cone depends on the length of focus necessary. It is best to have it a trifle larger than the length of focus required, thus allowing for making copies larger than the original. For a 5-inch focus lens the total distance should be about 12 inches, measured from the rear of the lens to the ground-glass. Circumstances and the construction of the particular camera which you are using must decide which is the simpler course. In any case, the most important consideration is to allow a largely increased distance between the lens and the focusing-screen. In some manner strive to arrange your camera so that the lens may be placed twice as far from the ground-glass as it is when ordinary landscape work is being done. If you can do this you will be able to copy the same size as the original. When this has been accomplished, copying becomes a very simple process. It is a matter of arranging the original in a good light (not direct sunlight), the camera in perfect line with the original and giving the correct exposure.
Proper Copying Light. If the atmosphere is perfectly quiet and there is no chance of the camera or the print being blown about, copying may be done out-of-doors. If the work is to be accomplished indoors, the original should face, or almost face, the window-not be along side of it-and the camera, of course, will be between the subject and the window, but at an angle. By this arrangement the visible grain on the paper, which is seen at its worst when the print to be copied is lit from one side, is done away with.
538. This texture or grain is caused by little particles of the paper standing out above the surface of the print. When the light comes from one side these little particles, standing out, will cast a shadow which will intensify the grain or texture and cause it to appear much stronger. Therefore, in order to avoid the grain in your negative, you must exercise care when lighting the original picture, lighting as broad and flat as possible. If the picture to be copied is very rough, or has a pebbled appearance, use a white reflecting-screen on the side opposite from which the strongest light comes. In this way the shadows of the surface are filled with strong light and they will not show so badly, if at all. Bear in mind too, that under-exposure also helps to show grain, for if the shadows do not receive enough exposure and the high-light and grain develop up strongly the shadows will be accentuated. The use of an extremely small stop is also apt to cause the grain to show strongly.