SET THE FILM SPEED, IF NECESSARY
Many modern cameras automatically set the film speed for you when DX-coded film is used. (The canisters of most modern films are imprinted with DX-coding.)
The exposure meters of some cameras (particularly older ones) must be set for the speed of the film you load. There is often a numbered dial with a film speed indicator ring that must be lifted and turned to match up with an arrow or other mark. The numbers, which are equivalent to the common speeds of film, usually begin at 6, 12 or 25 and end at 5000 or 6400. So, if you are using film with a speed of ISO 400, you adjust the dial so the arrow or mark is next to the number 400. Check your manual - or inspect the camera to locate the film speed numbers - to learn how to set film speed for your camera.
PRE-SET EITHER THE APERTURE OR THE SHUTTER SPEED
To keep things uncomplicated for this discussion, let's assume you are shooting a simple subject, like a picnic basket on a park table. Let's say you are fairly close to it so you can fill the frame, and that the lighting is bright, but diffused and even (no harsh shadows) because the sky is somewhat overcast. (We suggest these conditions because there will be neither dark shadows nor bright highlights in such lighting, and an averaging meter, center-weighted meter or any type of meter will achieve pretty much the same reading.)
You have a choice of either pre-setting shutter speed or aperture. (Check our sections under Shutter speed and aperture to learn the effects of choosing one or the other.)
Let's say you pre-set the shutter speed. Since there is no need to stop action with a fast shutter speed, your shutter speed can be safely set at 1/125 sec to capture this scene. (This is not the only shutter speed you can use, but it is fine for our purposes here.) Now, you have only to adjust the aperture to get proper exposure, and that is where your light meter comes in.
You may have preferred to pre-set the aperture rather than start with a specific shutter speed, something you might do if you were concerned about depth of field. So, let's suppose you choose an aperture of ƒ/8, which is sufficient for a scene that contains only one item to be photographed and therefore requires modest depth-of-field. In this case, you will use the light meter to tell you what your shutter speed should be to get proper exposure using an aperture of ƒ/8.
SWITCH ON THE METER
After checking to be sure you have fresh batteries in the camera, look through the viewfinder at the scene you wish to photograph, and focus the lens on your subject.
Switch on the light meter. Different cameras have different ways of doing this. In some, it is accomplished by pulling the camera's film-advance lever out a bit. In others, slightly depressing the shutter button will turn on the light meter. Still others have a separate light meter switch while some meters are always active.
CHECK THE EXPOSURE METER'S DISPLAY
Your camera's exposure meter display will indicate whether you must make an adjustment to get proper exposure of the scene.
There is such of variety of camera designs, with so many different means of displaying meter readings, that we can't cover them all here. However, measuring light using your camera's built-in exposure meter is usually simple to do, regardless of the type of display, once you know what you are looking for. Read your camera's manual to find out how it provides you with a reading. In some cases, you must adjust the camera controls (either the shutter speed or the aperture) until a needle is centered between two marks. With other cameras, two red indicators must light up simultaneously, or a needle must match up with the shutter speed you have selected. There are many different methods employed by various manufacturers. (The needles, lights, arrows and others markers are most all intended to show if you are over-exposing or under-exposing at a particular setting, and when they show neither over- or under-exposure, you are at proper exposure.)
If you do not have a manual and are unsure of how your camera's meter readings are displayed, take your camera to a photo shop and ask for assistance. Once you know what to look for, you will be ready to take an exposure reading.
If your meter display shows proper exposure right away, then you are ready to take a picture that will be acceptably-exposed. Odds are, however, that your meter display will show that an adjustment is needed.
In the case where you pre-set a shutter speed of 1/125 sec, you will need to adjust the aperture by turning the aperture control ring one way or the other until your meter display shows proper exposure. And, in the pre-set aperture example (pre-set to ƒ/8), you would adjust the shutter speed until your meter display shows proper exposure. That's it. Trip the shutter, and you will have a properly-exposed picture.
Note that it is not necessary to set either shutter speed or aperture before taking a meter reading. Both can be adjusted afterwards to achieve the desired results.
This description was purposefully simplified to help you get started by learning how to take a basic exposure reading with your camera's built-in meter. By reviewing other exposure-related sections of photographytips.com, you will soon be taking complicated exposure readings under different lighting and shooting conditions.
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