Canon EOS 1DS MARK II 9443A009 Instruction Manual (en)

Mirror lockup is enabled with C.Fn-12. (p.151) This prevents mirror 
vibrations which may blur the image during close-ups or when a super 
telephoto lens is used. Set Custom Functions with 
Press the shutter button 
The mirror will lock in the up position. 
Again press the shutter button 
The picture is taken and the mirror 
goes back down. 
If you take a picture without looking 
through the viewfinder, stray light may 
enter the eyepiece and affect the 
exposure. To prevent this, turn the 
eyepiece shutter lever as shown by the 
arrow to shutter the eyepiece. 
Mirror Lockup
Eyepiece Shutter
In very bright light such as at the beach or ski ground on a sunny day, 
take the picture promptly after mirror lockup. 
During mirror lockup, do not point the camera lens at the sun. The sun’s 
heat can scorch and damage the shutter curtains. 
Bulb exposures cannot be used with the self-timer. During the self-timer 
countdown, if you let go of the shutter button, there will be a shutter-
release sound. This is not the shutter release (no picture is taken). 
During mirror lockup, the drive mode will be single shooting (
) to 
override the current drive mode (single or continuous). 
After 30 seconds, the mirror lockup will be canceled automatically. 
Pressing the shutter button completely again locks up the mirror again. 
For mirror lockup, using Remote Switch RS-80N3 or Timer Remote 
Controller TC-80N3 (both sold separately) is recommended.