General Notes On Exposure Metering - Leica MP Manual

General notes on exposure metering

Most subjects normally have an even distribution
of dark and light subject details. Such normal sub-
jects reflect 18% of the incident light, correspond-
ing to a gray scale value to which all exposure me-
ters are calibrated.
If the subject actually reflects more light, e.g. a
snowy winter landscape, a yellow sandy beach,
bright house walls, or a white wedding dress, a
shutter speed and aperture setting in accordance
with the exposure meter display would result in
underexposure.
By contrast, subjects with predominantly dark de-
tails, e.g. a black steam engine, dark gray slate
roofs or a dark blue captain's uniform, reflect less
light and a shutter speed and aperture setting in
accordance with the exposure meter display
would result in overexposure.
In such cases, the exposure meter value has to be
corrected, if you are aiming for optimum exposure
results. This is not the case if you use selective
metering and take the measurement from part of
the subject with a good distribution of light and
dark details.
For example, in a wedding photo you would take
the measurement from the bride's face and not
the white wedding dress. For landscape photo-
graphs using a wide angle lens, the camera can be
pointed down until the LEICA MP's selective
metering field does not record the bright sections
of the sky.
If there is no suitable section of the subject to
measure in this way, it is necessary to use a com-
pensation factor, i.e. the shutter speed is extend-
ed by 2 to 4 times or the aperture is opened by 1
to 2 stops.
For sunlit snowy ground, for example, the com-
pensation factor is 4, i.e. instead of the metered
shutter speed of 1/1000s at f/8, the exposure
uses either 1/250 at f/8 or 1/1000s at f/4. For
less bright subjects, e.g. a bright beach, an com-
pensation factor of 1.5 is sufficient. The reverse
procedure is used for dark subjects.
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