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The method of calculating the angle of the camera
Calculated in units of measurement Feet
The width of the object obtained using a CCD camera with ¼ "and is 4mm focal length lens at a distance of 10 feet will observe how much?
The answer: H = D xh / f = 10 x 3.6 / 4 = 9 feet
Calculated in metric units
The width of the object obtained using a CCD camera with ¼ "and is 4mm focal length lens at a distance of 3m will observe how much?
The answer: H = D xh / f = 3 x 3.6 / 4 = 2.7m
Fixed lens: The focal length is fixed, for example: 4 mm
Varifocal lens: This type of lens allows you to adjust the lens focal length (mean angle) by hand. As the focal length is changed, we need to refocus the lens. The majority of this type of lens focal range 3.5 ~ 8mm
Zoom lens: The focal length can be adjusted within a range, for example from 6 ~ 48mm without taking interest in the net. The lens can be adjusted manually or by motor, so it can be controlled remotely.
In general, the camera network to adjust the amount of light entering the image sensor through the iris or adjustable sensor exposure time. In the conventional camera, the exposure time is fixed. Iris is the role of adjusting the amount of light passing through the lens. There are two different types of iris in the lens:
Iris is adjusted manually
Iris in manual focusing lens is usually used when the camera is installed in stable lighting conditions. The lens can not react to changes in light intensity so that the iris is attached to a "value range", each "value" is used in a certain light conditions
Iris auto calibration light
In outdoor conditions and areas with constantly changing light intensity, a lens with adjustable iris is automatically selected to be a priority.
The aperture of the iris is controlled by the camera and is constantly changing to optimize the sensor light went on.
DC-controlled iris: It is connected to the output of the camera, the iris is driven by the camera processor.
Video-controlled iris: iris is controlled by the video signal
F-number = focal length lens / iris diameter
F-number of a lens is the ratio of the focal length and lens diameter. It affects the amount of light entering the sensor accepts and plays an important role for images obtained
F-number the greater the amount of light entering the smaller sensor, otherwise the amount of light on the sensor will be larger and therefore the image quality will be better in low-light conditions yeu.Bang below illustrate some related values between f-number and volume sensor light is absorbed:
In light assembly limited to a neutral color filters in front of the lens. This reduces the amount of light entering the lens evenly across the entire visible spectrum and Iris forced open almost completely to compensate. Many of today's cameras integrated automatic iris control to ensure that the images are clear all year round even when the light intensity is constantly changing during the day.