CCTV cameras may specify their night time IR range as 10 or 15 m (wireless cameras), 20m or 30mm (small dome or bullet camera), 30m or 80m or more (large bullet camera, PTZ, etc.). In daylight or sufficient ambient lighting, almost all cameras will work well, but the more powerful the IR the better is the nighttime or low light range of the camera. Indoors generally 20-30m is good enough for most cases, but outdoors we may need 50m, 80m or even longer range. Therefore this has to be considered during the procurement stage only along with focal length tunings.
Please also note that while deploying such cameras with IR LEDs, ensure that no object/wall is very near in the field of view of camera otherwise it will scatter the IR, reflect it back into sensor and completely ruin the night time view making the camera unusable at night, till its mounting position is changed to get a clearance from that object. Some trouble some situations:
(1) If you have the camera looking through a window, the IR will bounce of the window.
(2) For cameras with a glass dome cover, you need to make sure the LED lights on the IR board are not being obstructed by the camera body. .
(3) Dirty Glass dome. Clean it with a damp microfiber cloth or windshield cleaner only.
(4) You have mounted the camera to close to a wall, ceiling, or in between two walls. In this case the camera's IR LEDs will be obstructed and cause IR reflection.
(2) For cameras with a glass dome cover, you need to make sure the LED lights on the IR board are not being obstructed by the camera body. .
(3) Dirty Glass dome. Clean it with a damp microfiber cloth or windshield cleaner only.
(4) You have mounted the camera to close to a wall, ceiling, or in between two walls. In this case the camera's IR LEDs will be obstructed and cause IR reflection.
(5) When you have an object too close to a security camera with infrared, it will cause that object to be over exposed because of the IR light shining off of it.
(6) IR LEDs attract spiders and insects, especially if camera is doing continuous recording (even though NVR will store only motion triggered recording) and is mounted near garden area. Spiders will create a web at night over the camera housing enclosing the lens. This will not bother you at daytime, but will show clouded view at night. It has to be cleaned periodically with a soft brush
Also worth noting is that higher the IR range, the more is power consumption. For eg.
A 30m IR camera may use 6W at daytime, 7-8W at night
A 50m IR camera may use 8W at daytime, 9-10W at night
A 80mm IR camera may use 8W at daytime, but use 11-12W at night which is very close to max powel levels of 802.3af
It maybe useful for deciding how many cameras to connect to any PoE switch, whose PoE capacity is often less than ports multiplied by maximum PoE (12.3 watts at PD, 15.5W at PSE) that can be supplied per port.
- Suman Kumar Luthra @ APRC-P3 Telecom Sub-Committee
No comments:
Post a Comment