This section is from the book "Modern Photography In Theory And Practice", by By Henry G. Abbott. Also available from Amazon: Modern photography in theory and practice: A hand book for the amateur.
We will endeavor to thorough explain the various kinds of cameras on the market. As we said before, box cameras are divided into two general types, those having a fixed focus and those having a bellows. Fig. 1 illustrates the Premo V, a cheap camera of the universal or fixed focus type. By a fixed focus is meant that this camera has no bellows to draw in or out, for the lens is of the single achromatic type, so that no matter whether you are taking a picture six feet or five hundred feet away, it will be in focus just the same. The term focus will be made clear when we come to a description of the practical use of the instrument. This camera, like all others that we shall describe, uses glass plates. The plate is inserted in the holder and the holder is inserted in the rear of the camera box, through a door made for the purpose. Then when the slide is pulled we are ready to take a shot. This camera has an adjustable diaphragm, having large and small openings for the admission of light. The shutter is adapted for both time and instantaneous work and the speed can be governed by means of a small lever at the front. The large central opening in the end is the lens and the two smaller ones at the top and side are the finders. The finder consists of a small lens and just back of it is a small mirror placed at an angle, so that the view is reflected upwards and is seen on the small piece of ground glass inserted in the top of the box. By shading the finder with the hand and pointing the camera in the direction of the object or scene to be photographed, a reduced image of the object may be seen on the ground glass and as the finder is made to coincide with the lens, the view we see in the finer is the one we will have on our plate. The finder gives the same view that the focusing screen at the rear does, except that the view is reduced in size and is not upside down as it is on the focusing screen. On the focusing screen, in the rear of a bellows camera, the view is transmitted by the large lens with which the picture is taken but in the finder it is transmitted by the small finder lens. Other cameras of this type have a bellows concealed in the box and this bellows is moved back and forth by a lever. Such cameras do not use fixed focus lenses and hence the necessity of focusing by drawing in or pulling out the bellows.
Fig. 2 illustrates the Premo Sr., a type of bellows or folding box camera. This instrument is first class in every respect and represents one of the very best types of cameras for the amateur. It is made in various sizes from 3 1/4 x 4 1/4 to 8 x 10. The 4 x 5 size is the most popular among amateurs in all makes of cameras. It is a great mistake for the novice to purchase a large camera. The larger the camera the greater the expense involved for plates, developing trays, washing and hypo boxes, paper, printing frames and mounts. A well chosen subject, properly exposed, developed and printed, in a 4 x 5 size, will always stand enlarging to 8 x 10 or larger. Mistakes and failures are bound to happen to all amateurs and for this reason it will found much more economical to use a small, rather than a large camera. Plates, paper, etc., for the 4 x 5 size are kept in stock by dealers in all parts of the world, while other sizes are not always to be had so readily. The Premo Sr., 4 x 5, when closed, measures 4 5/8 x 5 5/8 x 7 inches. Fig. 3 illustrates this camera when closed.
By pressing a concealed button at the top, the front falls down into position and is rigidly held there by a brace, which is shown at the right in Fig. 2. Just above the words Premo Sr. you will see a brass lever. This lever is connected with a cam and by turning it, as shown in the illustration, the front of the camera is bound in position. Push this lever to the left, (looking at the camera from the front) and draw out the bellows and clamp it in position by turning the lever as shown in the illustration. On the right hand side will be found a white celluloid scale and an index finger. The scale is for focusing when using the instrument as a hand camera. If the main object to be photographed is fifty feet away, you draw out the bellows until the index finger points to fifty on the scale. The small square box on the left is the view finder previously referred to and it is pivoted so it can be turned over when taking high or panel pictures. Two kinds of pictures can be taken, one which is four inches high by five inches wide and another which is five inches high by four inches wide. The camera is now in a position to take the former and in the event that we wish to photograph a church with a steeple, a high building or tall trees, we simply turn the camera over, with the view finder on top and turn the finder on its pivot. We will now get a picture which is five inches high and four inches wide.
This camera has a rack and pinion for fine focusing when using the ground glass. To the right and left of the bellows will be seen the two milled nuts which operate the mechanism. On the front board will be seen the lens, shutter and diaphragm and in order to examine and understand their workings see the enlarged view at Fig. 4. Ordinarily the diaphragm consists of a circular piece of metal plate with various sizes of holes cut through it and is also known as the stop. This camera has what is known as an iris diaphragm, similar to that in the human eye and this diaphragm opens and shuts by moving the small index at the bottom marked C. The use of the diaphragm will be explained later on. The center is occupied by the lens and as it is of the double variety, one half is located in front and the other half in the rear of the lens tube, leaving room for both the diaphragm and shutter between the front and back combinations. In the illustration the diaphragm is opened to a 16 stop and the shutter is also open. The circular plate above the lens is the shutter mechanism and dial. It will be observed that this dial is marked 100 - 25 - 5 - 2 - 1 - B. - T. If the dial is turned until the hand points to 100, then 1/100 second exposure will be made, if to 25 the 1/25, if 5 then 1/5, if 2 then 1/2 and if 1 then 1 second exposure. When the dial is turned until the hand points to B then the shutter will remain open so long as the pressure is ex-erted on the bulb, or if the hand points to T then one pressure of the bulb will open the shutter and the next pressure closes it. To manipulate the shutter, the lever A at the top is moved to the left, as shown by the dotted lines at F, until a click is heard. This winds the spring which sets the shutter in motion. The shutter can be released either by pressing upon the lever D or by pressing the bulb, which is shown in Fig. 2.