CCTV Cameras

Any Video Security System starts with CCTV security cameras. The images you see and record can only be as good as the images produced by your CCTV security cameras. Good security cameras produce good images and vice versa. There are several critical specification factors which affect the performance of your security cameras and consequently, the quality of your camera images. These factors also affect the price of security cameras. We offer a selection of CCTV security cameras to meet almost any situational need and budget. All our security cameras provide excellent specification factors, overall quality and excellent video images, coupled with very competitive prices.

Black and White (B/W) CCTV security cameras were the most widely used just a few years ago because of price and better light sensitivity. Today, color CCTV security cameras have narrowed the price gap and some of our color CCTV security cameras are as light sensitive as B/W security cameras. Because color video is more lifelike than B/W and provides much more positive identification, most CCTV security cameras purchased today are color units.

The main performance factors are:

The Type and Quality of the Imaging Chip in the camera: CCTV security cameras produce images using CMOS or CCD (Charge Couple Device) chips. Tiny and/or very low price CCTV cameras usually use CMOS technology, 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 Type of DSP (Digital Signal Processing) Chip in the camera: Digital CCTV security cameras use a DSP chip to digitize the analog video stream produced by the CCD chip, in order to improve certain picture quality elements and to add additional functionality. The DSP chip in the camera can have a very large effect on the quality of the video images produced by the camera.

Number of TV Lines: 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 370 TV Lines is generally considered good resolution while over 450 TV lines is considered high resolution. All our CCTV cameras have a resolution of at least 380 TV lines with many well over 400 TV Lines.

Light Sensitivity: Sensitivity ratings are generally 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 color cameras (i.e. B/W cameras will produce acceptable images in lower light conditions than color cameras). With the adoption of enhanced light sensitivity ExView CCD chips from Sony and Extra View CCD chips from Panasonic, we can now offer exceptionally light sensitive color cameras in both our Sentry and Mintron CCTV cameras. Our Sentry Day/Night cameras change from color to B/W when Lux levels drop below about 1.0 and produce useable B/W images down to a Lux level of about 0.03 Lux. We are also pleased to offer several Mintron cameras incorporating "frame integration". This method of electronically boosting the amount of useable light by holding the shutter open for longer, allows our "Starlight" cameras to produce a useable color image in as little as 0.003 Lux (the equivalent of the amount of light available on a starlit but moonless night).

Signal to Noise (S/N) Ratio: The higher the Signal to Noise ratio, the clearer the video image produced by the camera. Good CCTV cameras will have a S/N ratio of at least 48dB. Our Mintron color cameras have an actual S/N ratio of 60dB - much better than most while our Sentry cameras have S/N ratios of at least 50dB.

Camera Types:

Fixed (non moveable) CCTV security cameras come in two main styles: The first style has a camera body, to which lenses of different focal lengths and/or fixed or variable irises may be attached. The factors involved in choosing a suitable lens are given on the CCTV Camera Lenses page. Features such as BLC (Back Light Compensation), Auto Iris Drive and AES (Auto Electronic Shutter) on/off are provided, as is availability in several power inputs (e.g. 12V DC or 24V AC). New technology cameras now provide an "On Screen Display" (OSD) for choosing and setting functions. Because of their flexibility of configuration, body or box cameras are widely used in most commercial video surveillance systems.

The second style is basically a fixed lens mounted on a camera circuit board (board camera). These cameras may be packaged in a small case (Mini Cameras) or dome (Mini Dome) or tube (Bullet, Lipstick or Tube) or simply sold unpackaged, for mounting by the purchaser. Lenses in these cameras are either of a normal industry aperture or a "pinhole" lens of very small aperture. Pinhole lens cameras are often called "spy" cameras and may be mounted in a concealed way for covert surveillance purposes. Since the lenses in board cameras are pre-mounted, have a fixed iris and are usually of a short focal length (i.e. wide angle), their flexibility of usefulness is limited. However, this type of camera can provide a low cost solution in the right situation, particularly in a home or retail environment.

Pan, Tilt, Zoom (PTZ) Security Cameras: PTZ security cameras are able to rotate horizontally through 360°, vertically through 90° and have electrically powered zoom lenses capable of giving better than fifteen times optical zoom. Movement can be very fast and is controlled through a connected controller and/or through an appropriate DVR. In addition, PTZ cameras can be set to auto-scan or to move through a pre-defined range of pre-set positions and amounts of zoom.

New advances in technology now provide digital zoom in addition to optical zoom; day/night light sensitivity; intelligent movement that prevents too much incremental movement at bigger zoom factors and user definable movement “patterns” rather than guard tours consisting of numbers of presets.

PTZ security cameras are normally mounted in domes and when used outside, the domes are weatherproof and thermostatically cooled and heated. Vandal resistant domes are also available.

Once used almost exclusively by large corporations, governments and casinos, Pan, Tilt, Zoom (PTZ) CCTV cameras have now become much more affordable and offer better performance than just a few years ago.

Lately due to high demand cameras begin to come in in number of different designs.  Most popular once are dom cameras. Those cameras can be fixed or PTZ. Many of those cameras include such features as infrared illumination for night vision, mirrored cover to hide real direction of camera, vandal and weather proof design and materials.

Other popular design is a bullet cameras. Those small, easy blinded with surrounding cameras combine high reliability, quality and very sturdy structure.  Due to small size those cameras usually do not have PTZ capabilities.

CCTV Camera Lenses

It is important to use the right lens for the light conditions and desired field of view, otherwise the images seen and recorded will not be satisfactory. CCTV security cameras with an integral lens are less expensive but do not offer lens choices and are therefore limited in their usefulness. The important factors that govern the choice of lens are:

Focal Length: Lenses either have a fixed or variable focal length. Manually variable focal length lenses are called Vari-Focal Camera Lenses. Electrically powered variable focal length lenses are called Zoom Camera Lenses and while they are often used in high-end video surveillance systems, they are generally too expensive for use in most systems. The focal length of a lens is usually given in Millimeters (mm). Focal lengths of most CCTV camera lenses vary from 3.6mm to 16mm for fixed focal length lenses, to well over 70mm for zoom lenses. So what does that mean? In general, short focal length lenses (e.g. 4mm) have wide fields of view. This is good for close-ups or for seeing a large area. Objects appear smaller, rapidly, as distance from the camera increases. As lens focal length increases, the field of view narrows and more distant objects are easier to define. Take a look at the table below:

If, for instance, you wanted to be able to positively identify people, 25' away from a camera, a short focal length lens (e.g. 3.6mm) would give such a large field of view (37'x 26') that recognition would be uncertain. An 8mm or even 12mm lens would be far better.

The Lens Iris: CCTV security cameras that are used in good and constant light conditions (e.g. indoors with electric lighting) will perform satisfactorily with a "Fixed Iris Lens". Fixed Iris lenses with fixed focal length are the least expensive and the most widely used.

In varying light conditions (e.g. outside or inside facing a window) the iris on the camera will need to open and close to accommodate changes in light intensity, otherwise the camera images will be too bright or too dark. Lenses with electrically powered irises which automatically adjust as light conditions change are called "Auto Iris Lenses". They are more expensive but do a much better job in varying light conditions.

In constant light conditions that are either dim or very bright, a "Manual Iris Lens" may be the answer. As it's name implies, this type of lens can have the Iris aperture adjusted by hand to give the optimum camera image quality. Pricing for "Manual Iris" lenses is higher than Fixed Iris and lower than Auto Iris lenses.

The "F Stop" value of the lens: While "F Stop" is actually a ratio between focal length and lens aperture, in practice, when comparing lenses of the same focal length, it is an indication of the lens aperture. The smaller the "F Stop" the wider the lens aperture and the more light that lens will let into the camera. This is of particular importance in lenses with adjustable irises (both manual and auto). Our vari-focal, manual and auto-iris lenses have an "F Stop" value of 1.0, giving a far better aperture than most and consequently a better image, particularly in lower light conditions.

Materials are used from http://www.liquidcctv.com website.