User:Amitkumarsingh545/sandbox

CONCEPT OF IRIS IN LENS AND SHUTTER MECHANISM: Iris is responsible to control the intensity or amount of light from the environment incident over the image sensor to maintain the depth of view in the image whereas the shutter is responsible to define the exposure time or frequency of time for which the image sensor is exposed to light from the environment allowing the details of the image to be visible in highly moving environment. In a way function of both the mechanism is some or the other way same i.e. why in the fixed lens or fixed iris cameras shutter plays the role of iris as the light condition of the environment changes, we prominently call it as the Auto electronic shutter (AES) circuit.

Types of iris: Manual iris: the aperture opening can be manually controlled depending upon the amount of light incident from an object on sensor with to get appropriate depth of view in image.

NOTE: The shutter speed or exposure time in this case can be kept either manual or auto, depending upon the type of the object (moving or still) and amount of no light or excess light falling on the object. (For less light exposure time increases i.e. shutter speed decreases and for more light exposure time decreases i.e. shutter speed increases.

Application: few high end PTZ surveillance cameras bearing zoom lenses have this kind of feature wherein after zooming over the particular object, video might loose the depth of View. To minimize this effect, the iris aperture is controlled manually to adjust the opening to one of the 10-12 predefined presets (predefined F-stop values), in order to achieve closest depth of view, because the aperture opening value or F-STOP values hold specific numbers (10-12) which are fixed and won't change frequently with the changing focal length of lens, even if it is done manually, the image lacks the proper depth of field for higher focal length value to some points of focus, wherein foreground or background either of one loses the focus while viewing. Same is true for auto iris functionality. Hence after achieving the desired depth of view in the image, few objects bare strong light falling on the object causing the image to wash out, now we can use shutter (in auto or manual mode) to control the light falling on the sensor as changing the iris might cause the image to loose depth of view.

For low light environment, the max iris opening or lowest F-STOP is achieved by increasing the gain factor (AGC) to generate color image with minimum light in the environment, beyond this the image sensor is triggered to night mode along with the IR correction done either through IR cut filter circuit (as in economic fixed or vari-focal cameras) or electronic day or night mode switching circuit (as in low illumination or dark fighter cameras) generating Black and white image (only allowing the IR light to pass through IR corrected lens, other lights are discarded by the sensor).

Auto iris: are of 2 types video driven and DC Driven iris

DC driven iris: in this technology, the iris opening and closing is controlled automatically by camera itself based on the light in the environment, by passing the DC supply via connecter to the aperture in the lens. shutter speed or exposure time is configurable (can be set to either auto or manual).

Video driven iris: is an old technology used to control the amount of light falling on the sensor, the camera itself provides a sample of the image to the lens which in turn adjusts the aperture opening automatically to get an optimum quality image. Image generated by video driven iris is better compared to DC driven iris lenses and is costlier than DC- driven iris.

Based on the type of lenses accordingly surveillance camera should be suggested.

Application: Auto iris lenses are used in surveillance box cameras bearing C or CS-Mount lenses, PTZ cameras (bearing zoom lenses) including dark fighter, light fighter series cameras too.

P-iris lenses: "precise" iris, as name itself indicate it's an auto iris lens which can precisely adjust the iris opening or closing based on the focal length and environmental light condition to attain maximum depth of field. The cameras supporting these lenses are different compared to normal lenses. Usually comes with box cameras.

Fixed iris lens: these iris are available in the fixed lens cameras bearing focal length ranging from 2.8mm to 12mm where the iris has fixed opening and cannot be changed based on changing light condition to achieve appropriate depth of view, hence here the job of iris is done by shutter to some extent whose speed or exposure time changes based on the environmental light conditions and during low light condition the fixed lens low lux cameras use AGC (automatic gain control) circuit in the sensor to attain the light level from the environment for the sensor to generate image also there is 3D DNR (Digital Noise Reduction)Amitkumarsingh545 (talk) 06:27, 11 August 2017 (UTC) algorithm working inside these low light and low illumination cameras to compensate for the internal noise generated due to the AGC circuit in the camera in low light environment.

Note: Using the 3D DNR functionality in the camera bearing maximum noise during low light condition, might cause the image to loose the sharpness. instead using the cameras bearing the advance sensor with lesser amount of internal noise is preferable.

Application: used in fixed (M12 mount lens) and vari-focal (Φ14 mount lens) lens bullet and dome cameras.

Shutter Speed in surveillance cameras: what is shutter, where is it present in the cameras, what is it's role in the surveillance camera ? Shutter is present in the camera sensor which frequently opens and closes to capture the image or frame by the sensor to generate the stream of videos by combining these individual frames. higher the shutter speed lesser is the exposure time, more accurate details captured in fast moving environment with sufficient light in the environment but more light than the required ones, will cause horizontal stripes in the image and if lesser the shutter speed higher is the exposure time, hence less accurate details captured in the fast moving environment with sufficient light, but more light than the required ones, will cause accurate details to be captured in the fast moving environment at lower shutter speed.