Back Focus Adjustment; Iris Gain Adjustment - Canon CN20x50 Series Operation Manual

3 ADJUSTMENT

3-1. BACK FOCUS ADJUSTMENT

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

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 using a
small screwdriver.
Iris Operation Mode
Change-over Switch
Clockwise
(to increase gain)
Iris Gain Adjusting
Trimmer
This adjustment can be performed on the information display. Refer to the "Information Display Manual".
Loosening
Flange Back
Lock Screw
Rubber Cap
1
Select an object at an appropriate distance (approx. 5 to
7m). 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.
1
Pull up the rubber cap on the iris gain adjusting trimmer.
2
Set the iris operation mode change-over switch to the "A"
(Auto) position.
3
Turn the iris gain adjusting trimmer, using a small screwdriver.
As you look at the lens iris ring, set it to the position of
maximum gain at which no focus hunting occurs.
4
Put back the rubber cap after adjustment completes.
E7
3 ADJUSTMENT