Since some of you may know very little about photography, I will try to explain some of the basic photographic facts that you will need to know for better results.
First, as mentioned earlier, an SLR is simply a camera that allows you to view the subject through the lens just as the image will appear on the film. Most instamatic-type cameras use a second lens for the operator's view. This view may be slightly different from the image that will transfer to the
Most SLR cameras have a built-in light meter. This light meter will indicate the shutter speed the camera suggests for a proper exposure. Those cameras with an automatic exposure will use this shutter speed when the camera is set in the automatic mode.
The shutter speed can be set manually and usually with a latitude from 1 second to 1/1000th of a second. Most cameras will have the 1 second shutter speed setting indicated by a different color than the fractional shutter speed settings. These settings will be indicated as follows:
The numbers from 2 through 1000 are fractions of a second. For example, the 15 will indicate 1/15th of a second; the 250 will indicate 1/250th of a second. The higher the number, the shorter period of time the lens will be open. A shorter exposure time (lens opening) means less light
exposing the film.
Some cameras may have a 2-second setting, which will usually be in the same color as the 1-second setting. Also, most of the SLRs will also have a setting marked ?B.? This setting would indicate that the shutter release cable (sometimes referred to as a bulb) would totally dictate how long the shutter will remain open. When the shutter release cable is depressed, the lens will open, and it will not close until the cable is released. This would enable you to have an exposure of 5 seconds, 10 minutes, or whatever. Another important setting on the camera is the film speed. This adjustment is usually marked by numbers such as 25-64-100-200-400-800. There are often micro adjustments between these numbers which would allow you to set the ASA between these speeds. There are some cameras which allow you to set the ASA lower or higher than the numbers that I indicated. Still other, more modern cameras will make this setting automatically by reading a code on the canister of the film.
The film speed setting is critical only when using either the automatic mode or if the camera's internal light meter is being used as a guide. The lens on the camera also has an adjustment with numbers in a graduated scale. This scale
measures the lens opening (or aperture). This scale will usually indicate numbers such as 2.5 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32. The different aperture settings adjust the amount of light being allowed through the lens opening. Using a given shutter speed, an aperture setting of 5.6 will allow basically twice as much light through the lens as will a setting of 8. A setting of 8 will allow twice as much light
as a setting of 16. A very important fact to remember here is that the higher the number, the smaller the opening, and consequently, the less light that is allowed through the lens.
The aperture also controls something called "depth of field." This is simply the distance in front of and behind the focused point that will remain in sharp focus. The higher the number, the greater depth-of-field (greater distance in front of and beyond the focused point which will remain in focus). This is very important with coin photography, especially when taking macro (full-coin) shots. A smaller (higher number) aperture would allow more latitude with the focus, which can sometimes be tricky.
A proper aperture, shutter speed, and film speed are all required to produce a properly exposed photograph. Most SLR cameras are aperture priority, which means that once the lens opening is set and the ASA rating is set, the camera's internal light meter will determine the time required for a
proper exposure. An exposure- priority camera (of which there are few) would indicate that the camera will adjust the aperture depending upon the exposure time set and the amount of light entering the camera.