Canon CINE-SERVO 17-120mm T2.95-3.9 EF User Manual - Page 45

3 ADJUSTMENT 3 ADJUSTMENT 3-1. BACK FOCUS ADJUSTMENT OF THE LENS If the relation between the image plane of the lens and the image plane of the camera is incorrect, the object goes out of focus at the time of zooming operation. Follow the procedure below to adjust the back focus of the lens. Flange Back Adjusting Ring Loosening Flange Back Lock Screw 1 Select an object at an appropriate distance (1.5 to 3m recommended). Use any object with sharp contrast to facilitate the adjustment work. 2 Set the iris fully open. 3 Set the lens to the telephoto angle by turning the zoom ring. 4 Bring the object into focus by turning the focus ring. 5 Set the lens to the widest angle by turning the zoom ring. 6 Loosen the flange back lock screw, and turn the flange back adjusting ring to bring the object into focus. 7 Repeat steps 3 to 6 a few times until the object is brought into focus at both the widest angle and telephoto ends. 8 Tighten the flange back lock screw. 3-2. IRIS GAIN ADJUSTMENT An iris gain adjusting trimmer is located on the front of the lens drive unit. The iris gain is set appropriately at the factory. However, if you wish to change the iris gain, adjust the trimmer through the procedure described below. Iris Operation Mode Change-over Switch 1 Pull up the rubber cap on the iris gain adjusting trimmer. 2 Set the iris operation mode change-over switch to the "A" position. 3 Turn the iris gain adjusting trimmer, using a small screwdriver to set the level as desired. To determine the maximum gain, set the trimmer at a level where no hunting occurs. 4 Put back the rubber cap after adjustment completes. Iris Gain Adjusting Clockwise Trimmer (to increase gain) Rubber Cap This adjustment can be performed on the information display. Refer to the Information Display Manual. E7