Canon EOS-1DX Af Setting Manualbook page 122

Using ISO Auto
Minimum shutter speed at
ISO Auto expanded to
1/8000 sec.
Up to now, [Min. shutter spd.] was
1/250 sec., however this has been
expanded to 1/8000 sec. In Av and P
modes, you can now shoot with reduced
subject blur and camera shake due to
high shutter speeds.
Reduce camera shake and subject blur
at high shutter speeds in Av and P
modes
Another function added to ISO Auto is an expanded
shutter speed for [Min. shutter speed]. The minimum
shutter speed that was previously 1/250 sec. is now
expanded to a maximum of 1/8000 sec. By setting a
high shutter speed above a certain value when in ISO
Auto you can capture quick-moving subjects with
reduced blur and prevent camera shake. Use this to
reduce blurring when shooting in Av and P modes.
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