Canon EOS-3 Instructions Manual page 113

This is suited for slide films which have a narrow exposure latitude.
The shutter speed and aperture can be set in the familiar full-stop
increments.
Suited for negative films which have a wide exposure latitude.
EF 50mm f/1.0L USM,
EF 200mm f/1.8L USM,
EF 400mm f/2.8L USM,
EF 500mm f/4.5L USM,
EF 1200mm f/5.6L USM,
This prevents the focus from being thrown off by inadvertent turning of the
focusing ring after One-Shot AF.
When this Custom Function is set to 0 or 1 and Custom Function CF-4 is
set to 1 or 3 (see page 122), the focusing ring can be used to focus
before AF operation. However, this is disabled with this setting.
* When this Custom Function is set to 1 or 2, you must first set the lens
focus switch to MF (or M) to focus manually.
You can see how many frames are left in the roll.
Remarks
EF 85mm f/1.2L USM,
EF 300mm f/2.8L USM,
EF 400mm f/2.8L II USM,
EF 600mm f/4L USM,
EF 28-80mm f/2.8-4L USM.
Custom Function Settings
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