Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 428)

3 Custom Function Settings
428
Tv: Shutter speed
If you perform 1, 2, or 3, a slower shutter speed will automatically
be set to compensate for the number of stops the maximum
aperture has become slower. The same exposure that would be
obtained without performing 1, 2, or 3 is thereby obtained. The
shutter speed will change automatically within the range set with
[
8 3: Set shutter speed range ].
This function also works in the reverse of the above: When the
maximum aperture f/number changes to a smaller number (larger
aperture opening).
This function does not work with macro lenses whose effective aperture
value changes when the magnification changes.
This function does not work during movie shooting.
If [ ISO speed ] is set and the exposure cannot be maintained within the
range set with [ Range for stills ], the same exposure that would be
obtained without performing 1, 2, or 3 cannot be obtained.
If [ Shutter speed ] is set and the exposure cannot be maintained within
the range set with [ 8 3: Set shutter speed range ], the same exposure
that would be obtained without performing 1, 2, or 3 cannot be obtained.
If you perform 1, 2, or 3 and the camera turns off (power switch is set to
<
2 >, etc.) while the exposure is being maintained, the standard
exposure will be updated to the exposure at the moment the camera
turns off.
This function also works with changes in the highest f/number (minimum
aperture).
With [ ISO speed ] or [ Shutter speed ] set, if you perform 1, 2, or 3 and
then return to the state before performing 1, 2, or 3 without manually
changing the ISO speed, shutter speed, or aperture, the original
exposure setting will be restored.
If [ ISO speed ] is set and the ISO speed increases to an expanded ISO
speed, the shutter speed may change to maintain the exposure.