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.
Unable To See Image In The Finder. You have probably looked into the finder at the wrong angle; the camera was pointed toward the sun; or direct sunlight fell on the top of the finder. Almost all finders have a little hood that must be raised to shield it from the strong sunlight. You will be able to see in the finder a clear image of the object in front of the camera by shading the top of the finder with your hand (care must be taken that your hand does not cover the little lens in the front of the finder) and looking straight down on the finder. If you are pointing your camera away from the sun there is very little danger of the sun striking the finder, and you will have no trouble in seeing the image.
Unable To See Image On The Ground-Glass. You have not excluded enough white light with the focusing cloth; the focusing cloth may be too thin; perhaps you have not opened the shutter so that the light can enter the camera; the diaphragm in the shutter may be at the smallest opening, thus not admitting very much light. Do not look through the ground-glass. To view the image on the ground-glass be sure that the lens is wide open (using the largest "stop" or diaphragm) and allow no light to strike the ground-glass with the exception of that which comes through the lens. If you use a small stop the image will be much more indistinct on the ground-glass. Do not try to look through the ground-glass, but look on it, as though you were looking at a mounted picture. A little practice will readily overcome any difficulty you may experience at first in locating the image on the ground-glass.
Cannot Secure A Sharp Image. If the image is not sharp, the difficulty lies in not having the lens at the correct distance from the ground-glass (dry plate or film). If your camera has a ground-glass, proceed to focus as previously instructed, and rack the bellows backward and forward until the image is sharp, then lock the lens support in position.
Image Not Sharp When The Camera Is Used As A Hand Camera And Set At The Correct Distance Indicated By The Scale. If the pointer registers at the proper figure on the scale indicator, and the image secured on the developed negative is indistinct - blurred - the trouble lies in the scale of distance not being in proper location. For method of corrections see paragraphs Nos. 75 to 78 of this instruction, which fully explain how to proceed to correct the position of the scale.
Distortion Of Perpendicular Lines Of The Picture. In taking a picture of a building, and especially when the sides of the structure come near the edges of the negative, a distortion often occurs - the outside walls of the building being in the shape of a pyramid. This is caused from tilting the camera upward, which brings the lower part of the ground-glass or plate nearer to the building than the top of the ground-glass or plate. To avoid distortion of perpendicular lines of a building, the ground-glass or sensitive plate must always be absolutely parallel with the building or perpendicular to the ground. If possible, and especially where the building photographed is very tall, it is advisable to both raise the lens and use the swing-back or swing-bed. This same difficulty will appear should you point the camera down, although the pyramid effect will be reversed and the method of handling and correcting the distortion correspondingly regulated.