Canon EOS 1D Mark III Instruction Manual page 95

Shutter Speed Display
The shutter speeds from "8000" to "4" indicate the denominator of the
fractional shutter speed. For example, "125" indicates 1/125 sec. Also, "0"5"
indicates 0.5 sec. and "15"" is 15 sec.
If the maximum aperture blinks, it indicates
underexposure.
Turn the <6> dial to set a slower shutter
speed until the aperture stops blinking or
set a higher ISO speed.
If the minimum aperture blinks, it indicates
overexposure.
Turn the <6> dial to set a faster shutter
speed until the aperture stops blinking or
set a lower ISO speed.
s: Shutter-Priority AE
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