Nikon Autofocus Speedlight SB-24 - Manual (Page 8)

NOTES
Do not fire flash near the eyes; doing so may injure the
retina. Do not touch the flash head when firing the SB-24;
it may be hot due to normal operation. Also, be sure to
keep plastics and other delicate materials away from the
flash head when hot.
Nikon cannot be responsible for malfunctions or other
problems resulting from the use of other manufacturers'
flash units, cameras or accessories, including external
power sources.
In certain cases, due to normal characteristics of the built-
in microcomputer, the speedlight may not operate or an
abnormal display may appear, even with fresh, properly
installed batteries. If such a case occurs, turn off the flash
and remove the batteries, then reinstall batteries and turn
the power on. This should properly reset the computer.
“Red eye” is a common problem in flash photography.
Normally, flash pictures are taken when the surrounding
light is dim, and under such conditions the subject's eye
pupils will be dilated (open very wide). Red-eye effect
occurs when light from the camera’s flash reflects off the
interior of the eye and back into the camera’s lens. The
wide-open pupil allows much light to enter, and as a result,
the center portions of a subject's eyes can appear bright
red (white in a black and white picture). It is interesting to
note that the intensity of the red-eye effect varies among
individuals, and with two people in the same photograph,
one may have red-eye and the other may not.
The appearance of red-eye is also based on the angle at
which the light flashes on the subject and is reflected back
to the camera's lens. If the angle is 2 to 2.5 degrees or
narrower, the red-eye will occur. As you move closer to a
subject, the angle becomes wider, and the likelihood of
red-eye effect decreases. As you move farther from a
subject, the angle narrows and the incidence of red-eye
increases. When you get very far from a subject, the size
of the eye in the picture may become so small that red-eye
is not apparent, but when you switch to a lens with a
longer focal length, the subject becomes bigger and red­
eye may become apparent.
With an angle exceeding 2.5 degrees, red-eye is not likely
to occur. For example, with a 35-55mm range lens and
when standing about 1.4m (4.5 ft) or closer to the subject,
the angle between the flash and lens exceeds 2.5 degrees
and red-eye effect will most likely not be visible.
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