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Video Surveillance vocabulary


On November 3, 2014 By admin

The video surveillance industry can be a little confusing. If you are thinking about buying a video surveillance system for your business, make sure you are familiar with all the terms used. We know that some of the video surveillance terms can be a little confusing, which is why we have compiled a list of terms you can review and become familiar with. If you have any questions relating to video surveillance systems or terms you may not understand, feel free to give us a call and we can help answer your question!

Angle of View – Diagonal, horizontal or vertical view.

Aperture – the opening of the lens that controls the amount of light embracing the surface of a pickup device. The size is controlled by the adjustment of the iris.

Aperture Scale – referred to as an F-number. The international scale is: F1, F1.4, F2, F2.8, F4, F4.6, F8, F11, F.16, etc.

Aspherical Lens – lenses which one or more of the elements has a non-spherical surface.

Auto-iris Lens – electronically controlled iris on a lens. This allows the lens to maintain one light level during various light conditions.

Automatic Gain Control – or AGC, is an electronic circuit that augments the video signal when the strength of the signal falls below a given value.

Back Focus – the relationship of the distance of the lenses to the image device. This distance is important in order to maintain the right depth of field through changing focal lengths and varying light conditions.

Back Light Compensation – also known as BLC, a function of the camera that compensates for excessive light directed at the camera causing the video to bloom or causing the images in front of the light to be unusable.

C-Mount – an industry standard for mounting a lens to a camera where a 1” x 32” thread is used and the distance from the image plane is 17.52mm from the shoulder of the lens.

CS-Mount – a newer industry standard for mounting a lens to a camera where a 1” x 32” thread is used and the distance from the image plane from the shoulder of the lens is 12.52 mm. You cannot use a CS-Mount with a C-Mount.

DC Type Auto Iris – an auto iris lens in which the iris is controlled by the circuitry of the camera.

Depth of Field – the regions in front of and behind the focused distance where the image stays in focus. When you have greater depth of field, more of the scene near to far is in focus.

Extension Tubes – spacers used between the camera and lens to reduce the minimum object distance.

F-Number – this number expresses the brightness of the image formed by the lens controlled by the iris. The smaller the F-number the brighter the image.

F-Stop- used to express the speed of the lens. The smaller the F number, the greater amount of light passes through the lenses.

Field of View – the horizontal or vertical scene size at a given length from the camera to the subject.

Focal Length – the distance from the middle of the lens to a plane at which point a sharp image of an object viewed at an infinite position. The focal length controls the size of the image and angle of FOV seen by the camera through the lens.

Hunting – an industry term used to describe an auto-iris lenses inability to stabilize under particular light conditions.

Iris – the iris is a mechanical diaphragm which can be controlled manually or automatically to adjust the lens aperture.

Level Control – used to set the auto-iris circuit to a video level desired by the user. Turning the level potentiometer toward the higher position will open the iris allowing more light to pass through the lens, towards the low will close the iris allowing less light to pass through the lens.

Minimum Object Distance – also known as MOD. The closest distance a given lens will be able to focus upon an object.

Pinhole lens – lenses used mostly in covert applications where the camera/lens needs to stay out of sight.

Spot Filter – a neutral density filter placed at the center of one of the elements to increase the high end of the F-stop range of the lens.

Telephoto – a term used to describe lenses with a high focal number causing the reproduced image to appear larger than human eye reproduction.

Tracking – the ability of a zoom lens to remain in focus throughout the whole zoom range.

Video Type Lens – an auto iris lens with internal circuitry for processing of the video signal, which is in control of the iris movement.

Zoom Lens – a lens with the ability to change its focal length manually or with the use of a controller.

Zoom ratio – the ratio of the starting focal length to the ending focal length of a zoom lens.


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