Lens Chart
Lens:The lens determines the field of view the camera provides. Lenses range from 2.8mm to 18mm on an average. The larger the lens size the farther it will view. The draw back to a 12mm or 18mm lens is that the horizontal view narrows to as little as 15 feet.
*Many of our customers require a standard fixed wide angle 3.6mm lens. They are designed to be installed in a corner, provide a 90 degree field of view, and provide effective surveillance in a 30 x 30 foot area. If you need to adjust the angle and are not sure when viewing a cash register or looking down aisles, we recommend a vari-focal lens which you can adjust manually based on the angle and distance of the camera to the subject. For example, with a cash register we recommend a 4-8mm vari-focal lens so you can manually adjust and capture the money, hands, and register close up. When in doubt, go with a vari-focal adjustable lens. Lux and low lighting chart
During the day the amount of illumination reaching a scene depends on the time of day and atmospheric conditions. Direct sunlight produces the highest-contrast scene, allowing maximum identification of objects. On a cloudy or overcast day, less light is received by the objects in the scene, resulting in less contrast. To produce an optimum camera picture under the wide variation in light level (such as occurs when the sun is obscured by clouds), an automatic-iris camera system is required. Typically, scene illumination measured in foot-candles (ftcd)can vary over a range of 10, 000 to 1 (or more), which exceeds the operating range of most cameras for producing good quality video images. The chart above summarizes the light levels occurring under daylight and these low light level conditions. The equivalent metric measure of light level (lux)compared with the English (ftcd) is given.
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