Understanding CCTV Cameras FAQ

Understanding CCTV Cameras FAQ

This CCTV camera faq guide should help you choose security cameras to best suit your needs. If you want the most out of your CCTV system then this choice is critical to providing you with the security you need. This FAQ should explain some of the more complex and misunderstood aspects of cameras.


How does a camera work?

Like a human eye, light enters through the pupil (camera lens), then it hits the retina (image sensor) which processes the image into a signal. This signal is sent to the brain (DSP or chipset) where it is processed and adjusted depending on different light conditions.


What does TVL or television lines mean?

TVL is often misunderstood as the deciding factor on the quality of a camera. Unfortunately it’s not.


TVL is the number of horizontal lines of an analog camera’s resolution. While TVL is one of the most important resolution measures in a video system, a much more important factor in CCTV terms is ensuring you have the correct lens type for your application.


Your camera’s lens is the defining factor in quality and cannot capture detail beyond its own capabilities. If you had both a 420TVL camera and a 700TVL camera which both had the same lens then the 700TVL camera wouldn’t be able to see much further than the 420TVL. You may have a slightly better picture due to the increase in resolution but if you can’t read a number plate at 20m using the 420TVL then the problem is the lens not the resolution.


Do I need Fixed or Varifocal?

A fixed lens camera is one that cannot be adjusted to zoom in and out and is normally used for indoors or monitoring closer areas. Fixed lens cameras are normally a cheaper choice and can save you some money if you don’t need to have a zoomed in view of an area.


A varifocal or vari lens camera has the ability to optically zoom in on an area. The variable focal length can be used to change from a wide angle view covering a large area to a narrow focal view to centre on a particular area at long or short range. This is a popular choice of self-installation as it is versatile and can easily be adjusted to suit your needs.


How does the lens focal length affect the image?

Often misunderstood as the diameter of the lens, this is the focal length of your lens (usually measured in mm).  In smaller focal length lenses the field of view is wider, allowing in more light. As the focal length increases less light can get through the lens which result in a narrower telephoto field of view and the camera detects a more detail from its target area. This works in a similar way to using a pair of binoculars.


Essentially this factor determines how much you can optically zoom in and out on a varifocal camera.



What’s the difference between CCD or CMOS?


CMOS (Complementary Metal Oxide Semiconductor) sensors are much cheaper to manufacture and produces images which need a lot more electronic cleaning up by the DPS chipset to produce a good quality image. They offer a cheap alternative for lower requirements. A big benefit to CMOS is that you can have larger resolutions above 700TVL.


CCD (Charge Coupled Device) sensors are more expensive to manufacture but produce a higher quality image which doesn’t need as much cleaning by the processor. Your high quality cameras will more than likely be using a CCD sensor, but at the time of writing this article CCD cameras are limited to a maximum of 700TVL.


Does the size of the sensor matter?

You will notice that most camera specifications will state the size of the image sensor. In most cases this will between 1/4” to 1” in size. You should be looking for the bigger the better. Smaller sensors mean that less light can hit then and are more likely to suffer from distortion or noise. Larger formats can gather more light, making them more sensitive and are able to produce a higher quality image.


What does DSP mean?

DSP or Digital Signal Processing refers to the type of processing chipset (or brain) featured in your camera. The DSP is responsible for filtering and/or compressing the continuous analog signal from your camera’s image sensor and converting to digital. It is then cleaned up and modified before outputting the signal. A like our cameras, a DSP chipset should be chosen specifically to complement the other components of your camera.


What is an IP Rating?

The Ingress Protection Rating (sometimes known as International Protection Rating), classifies and rates the degree of protection which an electronic device can withstand. This rating is used to determine if a camera is weatherproof and suitable for outdoor use or not. Ideally you should be looking for cameras with a rating of IP65 or higher for unsheltered outdoor use. For a full list of codes please see our IP Rating list.


What does the Lux level affect?

Lux is the unit of illuminance and luminous emittance, which measures luminous flux per unit area. In camera terms this refers to how much light is required for you to be able to see. The lower the Lux level the better your image will be in dark or poorly lit conditions. With higher quality DSP and sensor combinations resulting in lower Lux requirements will literally allow your camera to see in the dark!


Most of our cameras are able to see down to 0.01lux without infra-red lighting. But when used in conjunction with infra-red lighting produces amazing night vision without loss of quality.


What is the difference between optical and digital zoom?

Optical zoom capability is determined by the lens itself and will produce a true zoomed in image with an increase in detail quality. With digital zoom however, a section of the image is merely enlarged at the expense of quality, resulting in a pixelated and fuzzy image.


What are IR LEDs?

Infra-red LEDs are used to illuminate a dark area a dark area for viewing. As light levels fall, the infra-red lights switch on automatically changing the image to black and white. The majority of cameras on the market now feature Infra-red lighting, and with more LEDs you can usually expect an increase in illumination range.



What are the different types of camera?


-Dome cameras

Dome cameras are generally the most popular indoor choice of cameras thanks to their compact size options, motorised 360 degree rotation options as well as being sturdy and easy to install, you can see why. There are generally 3 main types of dome camera below.


-Internal Dome cameras

Internal dome cameras feature an additional ‘dome’ housing which is an advantage as you can’t knock the lens. This additional house can also come in a ‘blacked out’ form which can be useful for hiding which direction your camera is pointing. 


-Eyeball or “Eye” Dome cameras

Eye dome cameras are usually a sturdier choice with many featuring armoured housing which allows them to be vandal resistant with up to 95% protection. They are also very easy to install and have superior IR illumination. 


-PTZ/Speed Dome camera

These cameras can come in both open and internal styles, and feature electronic motor which can be controlled to look around or even zoom in and out using a controller. They used to be reserved for only large scale developments but have since become much more affordable.


-Bullet cameras

Featuring a bullet-like shape, these cameras are the classic choice. All of our bullet cameras feature IR illumination. They are suitable for indoor and outdoor use and can range from small, plastic housing up to large heavy duty armour-cased cameras.


-Box / Body cameras

Similar in appearance to bullet cameras, these cameras generally feature a square casing, hence the name, and are generally bulkier. Usually these cameras allow you to install different lens per camera.


Covert Pinhole Lens Bullet Camera

-Covert cameras

These cameras are small, easily hidden or disguised cameras, which might be a better, more discrete choice for your home. Despite their small size, our covert cameras are capable of a professional quality video feed. Some come predisguised as PIR sensors or smoke detectors and others you can use these cameras to fit them within walls, ornaments or even a coke can if you wanted. You are only really limited by how crafty you are at disguising these tiny cameras. Ideally you will want to find a balance between having visible and hidden cameras to cover all circumstances.