activated, either by pressing the shutter button halfway down or by cocking
the film advance lever partway.
Aim the camera at your subject, framing the scene the way you want it. The
in-camera meter will display an f-stop and shutter speed setting suitable for the
lighting conditions of the scene. The method of display varies with the camera
model. Note that the exact location where you point your camera or meter may
have a significant effect on the exposure settings.
If you have a fully automatic camera, you just have to compose the frame
and press the shutter button; the camera does the rest. However, for maximum
control, you will want to adjust either the f-stop or shutter speed (or sometimes
both) yourself. Remember that you don’t have to use the exact settings recommended
by the camera. You can use other settings, as long as the overall quantity
of light that strikes the film remains the same. Often, the camera will show
you the equivalent exposure: when you change either the f-stop or shutter
speed, the other adjusts on the meter display automatically. For example, if the
meter recommends f/8 at 1/60, you can use f/5.6 at 1/125 or f/11 at 1/30 instead.
You might want to use particular settings for creative effect—to achieve
greater depth of field, freeze subject motion, or create a blurry result.
A TTL meter produces very accurate readings, because the light is read and
evaluated after it passes into the camera. Therefore it reads only light that is
reflected from your framed subject, and also takes into consideration any reduction
of light reaching the film that sometimes occurs when you are using
accessories such as filters.
However, you can still get inaccurate exposure recommendations, even if
you are using a TTL meter. All meters can be fooled—and often are by certain
situations. They are only instruments that depend on the information fed to
them; sometimes you must interpret this information and make adjustments.
Also, correct exposure is not an absolute; the meter’s recommendations are
not always the best settings for a given situation. Sometimes you may produce
a negative that better suits your purposes by deliberately over- or underexposing
your film.
How Light Meters Work
To know how best to use a light meter, you must understand how it is designed.
Meters read the light in a scene and recommend an f-stop and shutter speed setting
that produces a middle gray, which is defined as the average gray on a scale
from white to black. In practice, this means that a meter is accurate only as
long as a scene has a balanced mix of shadows, highlights, and grays that average
out to middle gray. (Note that middle gray is sometimes called 18 percent
gray, because it reflects 18 percent of the light that strikes it.
So, no matter what you point the meter at, it sees only gray. This average reading
strategy works well enough most of the time. Look around you. Most scenes
include a range of tones from light to dark. However, there are plenty of scenes
that are not average, but are instead mostly light or mostly dark. For these
scenes, an unadjusted meter reading is likely to produce incorrect exposure.
For example, if your subject is wearing a white sweater and standing against a
white wall, the meter will still suggest f-stop and shutter speed settings to produce
an average gray. The sweater and wall will be rendered as gray, rather than white.
If your subject is all black, the meter still sees only gray, as well. This is why it’s
so important to consider which part of the scene you take a meter reading from.
Say your subject is a woman with black hair, a white sweater, and a gray
skirt. If you were to get close up and fill the viewfinder with only her hair, the
meter would only see a dark area of the subject and respond as if there were
less light in the scene than there really is. The resulting indicated meter reading
will suggest an f-stop and shutter speed combination to produce average gray,
perhaps f/4 at 1/125. If you take a picture using these settings, the hair will get
more exposure than necessary and therefore will be rendered as gray, not black.
If you fill the viewfinder with your subject’s white sweater instead, the meter
will see only a bright area of the subject and respond as if there is more light in
the scene than there really is. The indicated meter reading will once again suggest
an f-stop and shutter speed combination to produce average gray, say f/16
at 1/125. This time, however, the settings will not allow in enough light. If you
take a picture using this combination, the sweater will get less exposure than
necessary and will be rendered as gray, not white.
Finally, if you point your meter at the gray skirt, you would get still another
exposure recommendation to produce an average gray result. This f-stop and
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