CCTV security cameras produce images using CMOS or CCD (Charge Couple Device) chips. Low price CCTV cameras usually use CMOS technology and produce poor quality video and have very poor light sensitivity. Decent quality and better CCTV cameras use CCD technology.

The size of the CCD chip is normally 1/4", 1/3" or 1/2". As a rule of thumb, the larger the size, the higher the quality of the image produced and the higher the price. However, higher density 1/4" and 1/3" CCD chips can now produce as good an image as many older 1/3" or 1/2" chips.

The number of TV lines in the video produced by the security camera is a measure of picture resolution (sharpness). The larger the number of TV lines, the better the resolution and hence, overall picture quality. Over 420 TV Lines is generally considered good resolution while over 520 TV lines is considered high resolution. All our CCTV cameras have a resolution of at least 420 TV lines with many well over 480 TV Lines.

Monofocal lenses provide fixed focal lengths from super wide angle to telephoto depending on the camera format and intended application. Two types are available:

• Monofocal Fixed Iris for fixed lighting applications where cost is the most important consideration
• Monofocal Manual Iris for indoor use with stable or moderately variable lighting conditions

Varifocal lenses offer maximum flexibility in camera installations, requiring a wide range of focal lengths. Focal length adjustments can be made with a turn of the dial, virtually eliminating the cost and inventory problems associated with improper monofocal lens selection.

PAL and NTSC standards explained

Although video format is the same throughout the World, the video standard or electronic signal that is recorded on the VCR or DVR varies from country to country. The two most common video standards used are NTSC and PAL.

PAL is the predominant video system or standard mostly used in Europe and UK. In PAL, 25 frames are transmitted each second. Each frame is made up of 625 individual scan lines.

NTSC is the video system or standard used in North America, Japan and most of South America. In NTSC, 30 frames are transmitted each second. Each frame is made up of 525 individual scan lines.

Most of our cameras support both standards.

Sensitivity ratings are given as the minimum "Lux" levels, at which the camera will produce a useable image (1 Lux equals 1/10 foot candle). The lower the Lux number, the lower the light levels at which the CCTV camera will produce an acceptable image. In other words, the lower the Lux level rating, the more light sensitive the camera.

Lux level ratings and the amount of light entering the camera are inversely proportional, to the aperture of the camera iris and so are stated at a specific “F Stop” - Focal Length divided by Aperture.

A camera with a Lux rating of 1.0 at F1.4, will only have a Lux rating of 2.0 at F2.0. B/W security cameras generally have lower Lux level ratings than colour cameras, i.e. B/W cameras will produce acceptable images in lower light conditions than colour cameras.

BLC is used to help correct times, when the lighting behind an object that you are trying to view, is much brighter than the the object itself. A good example of this is an entryway camera. The light from the outside shines through the glass and is much brighter then the light that is inside the store. As the person walks into the store, they light that is cast on the is much darker the the light that is outside. This causes the camera to produce a very dark image with very little detail of the subject being viewed.

By using BLC, the brightness of the outside light will be reduced, to allow the subject to appear brighter and create a better detailed image of the subject. For another solution for entry way cameras look in to cameras that have a wide dynamic range ( WDR ).

Automatic Gain Control.

A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation.