Canon EF - Manual (Page 59)

BASIC OPERATION
same light as your main subject. Push in and hold the
AE memory lock button with your left thumb.
Return your right hand to the camera body and
release the shutter. The exposure you locked in will
be close to the proper exposure needed for a very
light or very dark subject.
• In practical terms, the exposure latitude of both
black and white and color negative film (from which
prints are made) is inherently large enough to
overcome almost all AE maladjustments which occur
in day-to-day shooting. Therefore, it is not man­
datory to use the AE meory lock button at all.
However, color transparency film has extremely
small exposure latitude and requires near perfect
exposure to produce good results. When taking color
slides, the use of the AE memory lock button in the
special situations previously described is strongly
recommended.
* A standard 18% reflectance gray card Is a much
more accurate surface to meter than the palm of
your hand. It may be purchased very inexpensively
from your local camera dealer and carried with you
for situations requiring nothing less than perfect
exposure.
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