We have recently added our camera buying guide which has a section specifically about the CCTV camera range. It's worth spending some time reading through the guides as they will answer most or all of the questions you might have. If you need help regarding a specific project please don't hesitate to get in touch, we are always happy to provide advice free of charge and without obligation.
People selling CCTV are often very misleading when it comes to CCTV camera range. They normally quote two figures, the number of TVL and the IR range. This might be called the nighttime range. IR range is a largely made-up number based on how far away from the camera Infrared light can be detected. It has nothing at all to do with the effective range at which detail can be filmed.
The distance at which detail can be captured using a camera is its optical range. Unfortunately, no one ever quotes it, they only quote the IR range. The optical range has nothing to do with how many TVLs the camera has or how bright the IR is, it all depends on what lens is fitted.
A DVR stores images as tiny dots or pixels. With D1 resolution you get around 400,000 pixels per image frame. With a wide-angle lens, the pixels spread apart very quickly as you move away from the camera and fewer pixels mean less detail is captured. Conversely, a telephoto lens concentrates the pixels and captures more detail further from the camera. Camera lenses are measured in mm, the smaller the number the wider the angle of view. 2.8mm or 3.6mm would be considered wide-angle.
There is no definitive answer, it will depend on your specific needs. With some systems the ability to identify people will determine detail, on other systems, it might be the ability to read a vehicle registration plate. When we quote optical ranges we base them on how far from the camera a vehicle registration plate can be read.
We have a page that shows HD1080P CCTV camera images with different lens options
A varifocal camera allows you to manually zoom in or out during installation. This means one camera is able to perform different jobs. It can be set to wide-angle or telephoto. This means you don't have to worry as much when buying the camera, you can balance the angle of view and detail captured once it is fitted. You just need to make sure you have the correct lens range, we can help you decide.
With fixed-lens cameras, you only get one chance, if it's the wrong angle you have to replace the camera. For that reason, we would always advise buying varifocal rather than fixed-lens cameras.
An approximate guide to the optical range of different lens cameras is the distance at which a number plate or a person can be identified using standard-definition CCTV. For HD1080P systems you can double these figures.