CCTV / Video surveillance

The type of camera impacts the quality of pictures received for monitoring or recording- therefore, the CCTV camera along with the lens is an important component of the CCTV system that helps capture images and convert those to electrical signals which are observed or recorded.

To ensure the camera effectively converts light into a video signal, all cameras require an optical lens to focus the light onto an image sensor located directly behind the lens inside the camera.

There is a wide variety of cameras and lens available for CCTV systems which make the task of choosing a system a little difficult. Here are some purchase considerations that need to be assessed when purchasing a camera:

• Lighting conditions: Image capture during day and night. The level of light has a direct impact on the quality of images.
• Position of camera: Indoor or Outdoor. Outdoor camera may require protective enclosures to resist weather and criminals apart from aluminum housing and sealed cable entry.
• Field of View: Wide angle or narrow angle- the distance within which objects are in focus.
• Focal Length: The distance between the camera and the objects to be recorded.
• Sensitivity and resolution: Sensitivity means a camera's response to lighting levels while resolution implies the picture quality or details in image produced by the camera.
• Colour or monochrome: Certain cameras can also switch between color and monochrome depending on lighting conditions. Monochrome cameras are best suitable for low light conditions.
• Price: The price of the camera as compared to the features, benefits and after-sales service.

CCTV cameras are broadly distinguished by the type of image sensor in the camera, namely: CMOS (Complementary Metal-Oxide Semiconductor) image sensor chip and the other more common type known as CCD (Charge Coupled Device) imaging sensor chip.

The key differences between the two types of image sensors are:

• CMOS cameras are relatively cheaper but do not produce clear images as CCD cameras do. CCD cameras provide exceptional clarity and high resolution images.
• The majority of CCTV cameras and video camcorders use a CCD imaging sensor, whereas CMOS imaging sensors are more commonly used in web cams, budget home security cameras and digital photography cameras.

The different types of cameras are distinguished on the basis of the features and benefits offered. Some popular types of cameras include:

• Indoor Dome Camera: Generally used indoors and provides a variety of configurations such as: standard color, day/night, and Infrared versions.

• Outdoor Dome Camera: Such cameras have protective enclosures or weather-resistant, vandal-proof casings with flexible lens options.
• Box Camera: The box camera can be mounted or enclosed as desired. The lens is screwed on the front surface of the camera and provides flexibility in terms of field of view requirements.
• Day/ Night Camera: Such cameras switch digitally or mechanically to suit lighting conditions such that image quality does not suffer due to change in light levels.
• Infrared Camera: This type of camera provides infrared illumination in conditions devoid of natural light. IR cameras have Light Emitting Devices (LED) that automatically illuminates the field of view to help capture images in black and white mode.
• PTZ Camera: PTZ is an abbreviation of Pan, Tilt, Zoom(PTZ) which offers the ability to focus in all directions and zoom as required.
• Covert or Specialist Camera: Such cameras are located hidden from the view of the persons being monitored in the specific camera coverage area.

The images captured by a camera are effective depending on the type of lens used. The primary function of the optical lens is to:

• Limit and focus light onto the image sensor of the camera.
• To control the depth of field of the image, either for a wide angle image or a narrow angle image depending on the distance of the object.

Auto Iris lens are generally used to automatically limit and focus light and is also recommended for varying light and weather conditions. Portable cameras usually have zoom lens to allow varying points or distances to be monitored effectively. A CCTV operator controls the zoom lens in a CCTV system.