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2 pupil coefficient: the luminous flux, expressed in F, measured by the ratio of the focal length f of the lens to the aperture D of the aperture. Each lens is marked with a maximum F value, for example 6mm / F1.4 represents a maximum aperture of 4.29 mm. The luminous flux is inversely proportional to the square of the F value. The smaller the F value, the larger the luminous flux. The scale of the aperture index sequence on the lens is 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, etc. The law is that the exposure amount of the previous calibration value is exactly 2 of the exposure value corresponding to the exposure value. Times. That is to say, the aperture of the lens is 1/1.4, 1/2, 1/2.8, 1/4, 1/5.6, 1/8, 1/11, 1/16, 1/22, the previous value is The root value of the latter value is 2 times, so the smaller the aperture index is, the larger the aperture is, and the larger the illumination on the imaging target surface is. In addition, the aperture of the lens is divided into manual (MANUALIRIS) and automatic aperture (AUTOIRIS). When used with the camera, the manual aperture is suitable for occasions where the brightness does not change much. The amount of light entering is adjusted by the aperture ring on the lens, and it is adjusted once. The auto iris lens is automatically adjusted as the light changes, and is used in outdoor and entrance lighting where the light changes frequently and frequently.
3 automatic aperture lens: automatic aperture lens is currently divided into two categories: one is called video (VIDEO) drive type, the lens itself contains an amplifier circuit to convert the video amplitude signal from the camera into the control of the aperture motor. The other type is called DC (DC) drive type, which uses the DC voltage on the camera to directly control the aperture. This type of lens only contains a galvanometer aperture motor, which requires an amplifier circuit inside the camera. For all types of auto iris lenses, there are usually two adjustable knobs, one is ALC adjustment (metering adjustment), there are two options for peak metering and average metering according to target lighting conditions, generally taking average metering files; The other is LEVEL adjustment (sensitivity), which makes the output image brighter or dim.
4 zoom lens: Zoom lens is divided into manual (MANUALZOOMLENS) and electric (AUTOZOOMLENS), manual zoom lens is generally used in scientific research projects and not in closed-circuit monitoring systems. When monitoring large scenes, the camera is usually used with motorized lenses and pan/tilt. The advantage of the motorized lens is that the zoom range is large, you can see a wide range of situations, you can also focus on a certain detail, plus the pan/tilt can be rotated up and down, the viewing range is very large. The motorized lens has various magnifications such as 6x, 10x, 15x, and 20x. If the reference focal length is known, the variable range of the focal length of the lens can be determined. For example, a 6x motorized lens with a reference focal length of 8.5 mm, the zoom range is 8.5 to 51 mm continuously adjustable, and the field of view is 31.3 to 5.5 degrees. The control voltage of the motorized lens is generally 8V~16V DC and the maximum current is 30mA. Therefore, when selecting the controller, the transmission cable length should be fully considered. If the distance is too far, the voltage drop caused by the line will cause the lens to be uncontrollable. The input control voltage must be increased or the video matrix host must be replaced with the decoder control.
[ Huaqiang Security Network News ] All day with the camera running around. Friends who take cameras to shoot things when you use your camcorder to shoot your favorite things and scenes don't know how much you know about the camera's hardware knowledge, and how much you know about the main performance indicators of this important part of the camera lens. Speaking of this knowledge should be known to every friend who likes the camera! Here we discuss the main performance indicators of the camera lens. 1 Focal length: The size of the focal length determines the angle of view, the focal length is small, the field of view is large, and the range of observation is large, but the distant objects are not clearly distinguished. The focal length value is large, the angle of view is small, and the observation range is small. As long as the focal length is selected properly, even objects far away can be clearly seen. Since the focal length and the angle of view are one-to-one correspondence, a certain focal length means a certain angle of view. Therefore, when selecting the focal length of the lens, it should be fully considered whether the observation details are important, or whether a large observation range is important. If you want to see the details, choose a long focal length lens; if you look at a close scene, choose a wide-angle lens with a small focal length.