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Exposure
Exposure
When determining the normal lens for the film size you are using, take the measurement of the diagonal of the film. In 35mm this is approximately equated to a 50 mm lens. The equivalent in a 4x5 would be a 150 mm lens, although the film diagonal is actually 161mm. Take your favorite 35mm lenses multiply their focal lengths by 3 and that will give you the equivalent focal lengths in 4x5 format.
For view cameras focal length may be discussed 2 different ways, either in millimeters or inches. For example, the focusing distance from the ground glass to the nodule of a 150mm lens is approximately 6 inches. Therefore a 300mm would be a 12 inch lens and 210 is an 8 inch lens, etc. Many of the older large format lenses are referred to in inches instead of millimeters. For many of my images, I use a 90mm lens. A 58mm lens works especially well for interior shots. Another lens that I use quite often is a 210 which is just slightly longer than normal.
A modern multicoated lens is sometimes preferable as the coating helps reduce flare and increases contrast in comparison to older non-coated or single-coated lenses. The size of the image circle is important, as that is the diameter of useable image area that is projected by a lens. This is generally measured on view camera lenses with the lens stopped down to F-22. Two lenses of the same focal length could have very different image circles. A larger image circle allows greater camera movements to be used. Some modern lenses with large image circles can be quite large and bulky. Older lens designs like the Zeis Protar, Kodak Ektars etc. are quite small and have good covering power, but at the expense of a smaller maximum aperture.
Angle of coverage is the angle formed by the lines connecting where the light leaves the rear of the lens to the opposite sides of the image circle. The image circle and angle of coverage are similar in concept. The angle of view should be at least 70 degrees to allow an adequate amount of movement from the lens. Cameras tend to have a lot more movement than lens coverage. Generally, lens coverage, size and cost tend to go hand in hand. When you really start taking full advantage of rising and falling beds some of the other movements, you'll find that coverage is very important and it is something that you should consider when buying a lens.
Because a view camera lens is manually operated you should become familiar with the different parts of the lenses and their functions. Lenses are contained in either a barrel or a shutter. A barrel mounted lens has aperture control, but no shutter timing the exposure. Exposure is made by setting the aperture on the barrel and then removing the lens cap or by covering the lens with a hat and then removing the dark slide from the film holder and taking your hat off the lens. This is the way it was done in the early days before the advent of shutters.
View camera shutters are a different than those in a 35mm camera. The shutter in a view camera is what is known as a leaf shutter, comprised of blades which open and close like the iris of the eye. This shutter must completely open before it can close. All the film is exposed at one time instead of in sections as with a focal plane shutter. The film receives most of its exposure while the shutter is wide open. One of the advantages of a shutter of this type is that a strobe light can be synced to exposure at any shutter speed.
The main shutter controls include the shutter speed dial which sets the speed. The shutter release trips the shutter. There is the cable release socket and the shutter cocking level. Most lenses you'll find also have a flash sync socket. The aperture lever sets the aperture of the lens. There is usually a press focus lever which allows you to close down the lens after focusing so you can insert your film holder and pull your dark slide before you trip the shutter.
The most commonly used shutter for view camera lenses today is manufactured by Copal. Other shutter manufacturers are Compor and Prontar. Some variations of shutter design are available. There are self cocking shutters that don't have to be recocked each time. But they usually have slower shutter speeds. Electronic shutters are also available.
Today's shutters come in three sizes depending upon the focal length of the lens and its maximum aperture. These sizes are a #0, a #1, and a #3. If you have older lenses for 8x10 or 11x14 view cameras they will frequently require larger shutters, such as a #4 or #5. Although these large shutters are no longer made, they can still be found. Look for shutters with the names Ilex, Acme or Betax. Try contacting S. K. Grimes.
The shutter speed designations on the newer shutters are usually designated T, B, 1, 2, 4, 8, 15, 30, 60, 125, 250, and 400 or 500. The T designation means the shutter will open when the cable release is pushed. To close the shutter you have to press the cable release again. The B shutter is similar to the B or bulb setting on a 35mm, as long as you push the cable release down the shutter is open, when you release it the shutter closes. The other speed designations correspond to fractions of a second. Modern shutters are mechanically operated and run by a system of gears and springs. If taken care of these shutters should last indefinitely, but they do need to be cleaned on occasion.
Older shutters have different shutter speeds. They are usually T, B, 1, 2, 5, 10, 25, 50. On older lenses you might run across what is termed a compound shutter. It is operated by forcing air pressure against a diaphragm, through a small tube at the top of the shutter. A compound shutter needs a lot of care and is not quite as reliable as a mechanical shutter. You can identify this type of shutter by the squeeze bulb which forces the air into the shutter.
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