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

Remove the eyecup. 
While grasping both sides of the 
eyecup, slide it upward to remove. 
Turn the dioptric adjustment 
Turn the knob to the right or left until the 
AF point or the center spot metering 
circle looks sharp in the viewfinder. 
Reattach the eyecup. 
To obtain sharp images, hold the camera still to minimize camera 
Firmly grasp the camera grip with your right hand, and press your 
both elbows lightly against your body. 
Hold the lens at the bottom with your left hand. 
Press the camera against your face and look through the viewfinder. 
To maintain a stable stance, place one foot in front of the other 
instead of lining up both feet. 
Dioptric Adjustment
Holding the Camera
If the camera’s dioptric adjustment still cannot provide a clear viewfinder 
image, using Dioptric Adjustment Lens E (10 types) is recommended. (p.169)
Vertical shooting
Horizontal shooting