When installing a zoom lens on a camera, you may find that the lens cannot be focused at either end of the zoom range. If this problem occurs, you may need to adjust the camera back focus. By adjusting the back focus, you are changing the position of the pick-up device in relation to the rear of the lens.

Procedure

1. Set up subject or test pattern 75 feet or more away from the camera. If this is not possible, choose the farthest object from the camera.
   
   
2. Important, set the iris at wide open. If the scene is too bright reduce illumination or use a filter to reduce the amount of light coming into the lens. If the iris is not set all the way open, objects that are in focus during the day may fall out of focus during nighttime viewing.
   
   
3. Adjust the focus at extreme far.
   
   
4. Adjust the zoom to extreme wide angle.
   
   
5. If the camera is equipped with a pick-up device or camera lens mount set screw, loosen the screw.
   
   
6. Adjust the pick-up device position screw or camera lens mount to obtain a clear picture.
   
   
7. Adjust the zoom to extreme telephoto.
   
   
8. Using the lens controller, adjust the lens for best focus. Do not adjust the camera!
   
   
9. Adjust lens back to extreme wide angle.
   
   
10. Readjust the camera for a clear picture.
    
    
11. Tighten the pick-up device or camera lens mount set screw to ensure it does not change position.
    
    
12. Repeat the above steps until the focus remains clear throughout the zoom range.
    

In most cases, changing a lens will not require this procedure. However, as lenses may vary from manufacturer to manufacturer, this procedure may be necessary.