TECH TIPS

May 2000 CCTV, Surveillance & Remote Monitoring

Cameras and lenses

Back focus adjustment

Note: The lens aperture must be wide open for all back focus adjustment procedures. Therefore, these procedures must be performed in subdued lighting or with the use of filters in front of the lens to reduce the light.

Fixed lens models (indoor method)

1. With the camera operating, view some object at least 20-25 m away.

2. Set the lens focus ring to infinity by rotating it fully clockwise as viewed from the front of the camera.

3. Set the lens iris to its widest usable opening. See note above

4. Adjust the imager position to bring the object being viewed into sharpest focus.

Fixed lens models (outdoor method)

1. Point the camera at some object which is more than 60 m away.

2. Set the lens focus ring to infinity by rotating it fully clockwise as viewed from the front of the camera.

3. Turn the camera on and hold an ND 3.0 metallised filter in front of the lens. Make sure the lens iris is set to the widest usable opening. See note.

4. Adjust the imager position to bring the object being viewed into sharpest focus (with filter in place).

Zoom lens models

1. With the camera operating, view some object at least 20-25 m away.

2. Make sure the lens iris is wide open. See note above.

3. Set lens focus to extreme FAR.

4. Adjust lens zoom to extreme WIDE angle. (Widest field of view.)

5. Adjust the imager position on the camera to obtain the best focus.

6. Move lens zoom to extreme TELEPHOTO. (Smallest field of view.)

7. Adjust lens focus (by the controller) for best picture.

Monitors

Recommended set-up of video monitors for maximum

CRT performance

Video monitors are designed to give the user a wide range of operation by providing externally accessible adjustments. These controls may include vertical and horizontal hold, vertical linearity and height and, most important, brightness and contrast. The key to achieving maximum life from the CRT (kinescope) is proper adjustment of the brightness and contrast. Operation of the CRT at excessive levels of brightness and contrast can shorten tube life and lead to premature failure.

To prevent this situation of operating above the required conditions for normal viewing of the video monitor, a simple procedure can be used. After the video monitor has been installed, set room lighting at the level which will exist during actual operation. Turn both the brightness and contrast controls to the minimum setting. Next, turn the brightness control up until a very faint glow can be seen on the CRT raster area. Allow your eyes to become conditioned to viewing this faint glow. Usually several seconds is adequate. Adjust the brightness control down until the glow just disappears and then turn the brightness up until the glow just reappears. Now that the brightness control is set, the contrast control can be adjusted. Turn the contrast control up until the video information can be seen. Adjust the contrast control up until a level is obtained for comfortable viewing of the screen. Do not set the contrast level high enough to cause smear. If present, smear will be evident in the white portion of the video screen.

Proper adjustment of the video monitor controls will extend the life of the CRT. Be kind to your monitor; it is a key ingredient of your system.

Source: Tech Tips provide extra technical notes developed by Philips' application engineers in response to user's applications questions.





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