is an electrical-mechanical device that can only provide
information for which it is designed. You are responsible
for translating this information into useful exposure
data.
Light meters are calibrated to see one shade
only-middle gray. This means the information that the
meter provides, no matter how much light is falling on
the subject or what the reflection characteristics are,
reads the subject the same as though it were middle or
neutral gray (18-percent gray). Theoretically, if you take
a reflected-exposure meter reading from an 18-percent
gray card and expose your film according to the reading,
the result should be a picture that matches the tone of
the gray card exactly; however, when you take a light
meter reading of a white or black object, the light meter
still reads the objects as though they were 18-percent
gray.
When you take a photograph that includes a gray,
white, and black card, you will see how, depending on
where you take the light meter readings, they affect your
photograph; for example, when you take the light meter
reading from the black card, the final picture reproduces
the black as middle gray, and the gray and white cards
as white. When you take the reflected-light meter
reading from the white card, just the opposite occurs. In
your final picture, the white card reproduces as middle
gray, and the gray and black cards reproduce as black.
This example demonstrates overexposure and
underexposure. When the reading was taken from the
black card, the meter raised the black tone to middle
gray, and the gray card tone was also raised so it
reproduced as white. Thus both the black and gray cards
were overexposed The opposite occurred when the
exposure was based on the reading from the white card.
The white tone was lowered to middle gray and the gray
card tone to black, resulting from underexposure. Only
a light meter reading taken from the gray card allows all
three cards to be imaged at their true tone.
A more practical example on the way a light meter
reads 18-percent gray is illustrated in the following
example. Suppose you are going to photograph a ship
alongside a pier. Bright sunlight is striking the ship from
the side, causing part of the ship to be in shadow. This
creates a brightness difference between the highlight
area and the shadow area. Both highlight and shadow
areas are equal in size and importance. When you get
close to the ship and take a reflected meter reading of
the highlight area alone, you expect the finished
photograph, like the white card in the above example, to
be middle gray. When you stop down the aperture to the
recommended exposure of the meter, you are also
reducing the amount of exposure from the shadow area.
This results in a loss of detail in the shadow area of the
ship, because it is underexposed. The opposite effect
occurs when you take a meter reading from the shadow
area. In this case, the shadow tones are raised to middle
gray and have detail, but the highlights are overexposed
and completely "washed out."
If, however, there was an area in this scene whose
tone was midway between the highlight and shadow
areas, you could use it to take your light meter reading
(like the gray card was used in the previous example).
In this example, assume there is no tone midway
between the two extremes. You can still get an accurate
light meter reading of the entire ship. Since the highlight
and shadow areas are of equal size, the average light
meter reading you get will represent a tone that is
midway between the two extremes.
REFLECTED LIGHT METER READING
VARIATIONS
There are variations of light meter readings used to
provide accurate light meter readings of different types
of scenes. These methods are as follows: the integrated,
or average, method, the brightness range method, the
darkest object method, the brightest object method, the
substitution method, and the bracketing method.
Integrated, or Average, Method
The technique of making reflected-light meter
readings from the camera position is called the
integrated, or average, method. This method was used
and explained in the examples above. This method is
accurate for the majority of photographs taken.
The integrated, or average, method of measuring
reflected light is acceptable for scenes that consist of
approximately equal portions of light and dark areas;
however, when a scene is composed of either
predominately light or dark areas, the meter reading may
not be accurate.
The reason for these inaccurate meter readings can
be more easily understood by using an example of
photographing a checkerboard with alternating
black-and-white squares. When the meter is held at a
distance to include the entire board, the reflected light
from both the black and the white squares influence the
meter, so an average reading results. The light measured
from this position is the integrated sum of both the white
and the black squares, as though the checkerboard were
one gray tone. The light meter reading from this point
should produce an acceptable image.
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