Canon EOS-1DS MARK III Instruction Manual page 69

Custom Function Settings
0: Normal (enable)
1: Disab{e _,O,Muit}-eontroi_er
When the power switch is set to <ON>, the <_>, <O>, and < _->
will be disabled from setting anything. The shutter button can still be
used to shoot. This prevents any settings to be changed inadvertently,
so it is convenient when you keep shooting with the same settings.
if you change the focusing screen, change this setting to match the
focusing screen type. This is to obtain the correct exposures.
0: _Ee-C {V
Standard focusing screen (Laseromatte)_
1: _EeoA, B, C, C I_, C H}, D, H, {, L
For Laser-matte screens.
2: _P:Ee-S
For Super Precision Matte screens.
3: _J Ee-N,R
For New Laser-matte screens.
-[he FPq E c-S focusing screen is optimized for lenses whose maximum aper[ure
is f 1.8 to f/2.8. If the lens maximum aper[ure is brighter than f/1.8, the center
spot me[ering circle and Area AF ellipse might become difficu t to see.
A}so. if the lens max mum apeRure s slower than f/2.8 the viewfinder will
ooK darker.
_ Even if all the Custom Functions are cleared, this setting will be retained.
Since the Ec-A. Ec-B. Ec-I. and Ec-L focusing screens nave a prism at
Lhecenter, correc-c exposures cannel De oD[alned with evalua(ive
metenng and center spo[ me[enng, use e_mer center-weighted average
metering or AF point-linked spol metering (except the center AF point).
To change the focusing screen, refer to the instructions ma[ came with
Lhefocusing screen.
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