Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 245)

Shutter Mode
You can choose the method of shutter release.
1.
Select [ : Shutter mode].
2.
Select an option.
Mechanical
Shooting activates the mechanical shutter. Recommended when shooting with the
aperture of a bright lens wide open.
Elec. 1st-curtain
Shooting only activates the second-curtain shutter. Camera shake may be suppressed
by [
Mechanical ] depending on the shooting condition. Note that in < > drive mode,
mechanical shutter is used for the second and subsequent shots.
Electronic
Enables you to shoot without a shutter sound.
In continuous shooting, the camera always shoots at high speed (up to approx.
20 shots/sec.). Also during continuous shooting, the white frame is displayed repeatedly.
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