game cams, page 2
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The Mechanics of Remote Cameras
Game cameras work on the same basic principle as motion sensing yard lights; that is, they employ a passive infra-red light or heat sensor which is designed to detect a significant increase in ambient background levels of infra-red light and/or heat. Contrary to popular belief, the more common commercial versions do not employ any type of emitted or projected light, infra-red (hereafter referred to simply as “IR”) or otherwise. Thus, even if a subject were capable of seeing in the IR spectrum, it would not be possible for them to see the IR detector on a game camera, as no IR light is projected. Game cameras only detect changes in the ambient IR level, which generally occurs when some heat source, such as a warm-blooded animal, moves into the detection zone.
This method of detection has positive and negative aspects in field use. The major plus is that simple motion of objects such as wind-blown trees, brush, or even insects generally cannot set the camera off. There are, of course, always exceptions. It occasionally happens that sun- heated trees, or even bare spots on the ground heat up fast enough to trigger the IR sensor on the camera, and trip the shutter. If your camera tends to have a lot of empty daylight shots, particularly in the morning or evening, this is almost always the reason. The fix for this is relatively simple: Try as much as possible to never point the camera east or west, into the rising or setting sun. The best direction is north, but in sufficiently shaded woodlands, this is not as critical. Try to avoid placing the camera in a location or direction where it will be pointing out into an open sunny area, from a more shaded or dark area. This type of arrangement tends to create false trips of the shutter as the more open area is illuminated during the daylight hours.
The “false positive” is relatively rare, when the sun’s position is taken into consideration. Cameras using passive detection of heat sources have the obvious advantage of reducing the likelihood of this type of incident, but they have a disadvantage also: They only work at relatively limited distances. While detection range varies among the various brands, it is a safe assumption that most do not work very well beyond about 90 feet, and often much less than that. For this reason, it is important to try and place cameras in such a location or position as to take these limitations into consideration.
Another limiting factor for many cameras is the distance to which the flash will illuminate. While some have flashes capable of illuminating out to 100 feet or more, most are somewhere in the neighborhood of 20 to 30 feet. This limited distance must be taken into consideration when cameras are set, as it is typically about half of the distance that the IR detector works; thus, at times, you end up with something triggering the camera, yet nothing is seen in the photo because the subject is far enough away from the flash to be out of the illumination range. To avoid this, we must try to place the camera as close as possible to the location where you hope the subject will cross or enter — the closer the better, to a point. Failure to do this will result in a lot of empty night shots where it is apparent that something triggered the camera, but nothing is visible on the photo itself other than the background, of course.
Other factors that may affect the end results are the height and angle at which the camera is set, and any vegetation that might be present within the camera’s field of view. Most cameras have some type of test function to allow you to locate the detection zone of the IR sensor and set the camera accordingly. The height of the set can effect this zone, with the best results generally coming from cameras set at about 3-6 feet off the ground; this can, however, be altered to fit different needs or desired results.
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