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The ability to film in low light conditions or even complete darkness is essential for many CCTV applications. Part of that ability is down to using the right electronics which are sensitive enough to work in low light, the other tool used is infrared or IR lighting. We have a guide to infrared in our camera buying guide.

Infrared light isn't visible to the human eye but CCTV cameras switch to black and white as light levels fall and can film the IR light spectrum. This means that to the camera it's like shining a torch. IR has to bounce off something but providing there is a hard surface to reflect the infrared your camera is able to see in the dark.

Previously cameras had separate infrared light lamps bolted onto the side of their housings. It made the whole unit very large and industrial looking. In more recent times cameras have been designed with IR lighting built into them. This greatly reduces their overall size and visual impact. It also reduces cost when compared to modular cameras using separate lighting units.

Many people selling CCTV cameras describe them in terms of the infrared range. Do not confuse this with the optical range of the camera or the distance at which a camera can record detail. That is determined by the lens. Wider angle lenses will have a shorter optical range, more telephoto lenses a longer range. The IR range is a largely immaterial figure, often made up and is supposed to represent the distance at which the camera's infrared can be detected. In reality, the ability of a camera is a combination of the lens, how powerful the IR is and how sensitive the electronics are.

Something you might see mentioned is an IR cut filter. This is a mechanical filter that moves in front of the camera lens during the daytime. The filter is designed to improve colour rendition during daylight filming. Electronic adjustments can also be made to the camera to improve colour representation.

We get a number of calls from people experiencing problems with their CCTV cameras at night. They install a CCTV system during the day then at night find they have issues. We have created this page to cover some of the most common symptoms and causes.

No image at night

The most extreme problem is seeing nothing at all on the screen. Check all the same things you would look at during the day. Make sure the camera has power, ensure all the connections are secure and that the infrared is illuminating (this will mean power is getting through to the camera). If that is all in order then stand in front of the camera quite close to it. Infrared needs to bounce off a surface back into the camera. If you just point the camera into space it won't see anything.

If you have bought a camera with a long-range, 20 or 30 metres plus from someone and you are expecting it to work at that distance don't rely on quoted specs. IR range is pretty much made up and shouldn't be used as a guide to effective range. You could be trying to film too far away. Stand closer to the camera and see if you can see an image. Failing that you may be suffering a voltage drop.

Voltage drop

One of the most common problems experienced is voltage drop. When the IR illuminates the power requirement of the camera increases, if the cable run is too long or there isn't enough copper you will experience a voltage drop. This could cause the camera to stop working altogether. It could also cause the camera to cycle on and off. The IR illuminates which causes the camera to switch off. The camera re-starts and works until the IR switches on again. You may also see image deterioration when a voltage drop occurs. If you are using CAT5 cable to join the cameras to the DVR and power supply make sure you are using a pure copper cable rather than CCA or copper-clad aluminium. Wire the cameras as per our guide to using CAT5 cable in CCTV. In particular, make sure you use 3 pairs of wire for the 12 volt supply.

A white screen or white areas on the screen

This is another common issue. If you see a white screen at night or a white haze then the most likely cause is infrared light reflecting back into the camera lens. The wider the angle of view the more chance there is of this happening. Have you got the camera's sun visor too far forward? We suggest having the rear of the visor in line with the back of the camera body. Is there something just out of shot but in front of the camera which can reflect IR back into the camera, guttering and soffits are common culprits? On vandal dome cameras check to make sure any sealing rings which fit between the lens and the inside of the clear plastic cover are securely in place.

Whilst you can't see the infrared light in the camera it is extremely bright and any surface close to the front of the camera can reflect the light back into the lens. Even if the surface is out of screenshot it can still reflect the IR. If you can't move the camera try zooming it in more so you narrow the field of view. Light pollution from other sources can also cause white areas to appear on the screen. Vandal dome cameras are particularly prone to corruption from external light sources.

A camera mounted inside a window produces a white image at night

Well, it will do. The glass is a reflective surface and is right in front of the camera. The infrared will bounce off the glass straight into the lens causing the camera to dazzle itself. It's a bit like taking a flash photograph in front of a window at night.

General image deterioration at night

When the infrared switches on the camera draw more current. If your power supply is not powerful enough this extra current draw could cause problems. Also, make sure you have not exceeded the recommended cable run length and that the cable is substantial enough. Voltage drops along the length of the cable and the thinner the cross-sectional area of the cable the more this happens.

General haziness of the image at night with some movement on the screen

Check the camera for spider webs. During the day you don't notice spider webs. The camera focuses beyond the web and it appears invisible. At night the infrared bounces off the web and it shows very clearly. We do sell a spider spray to help reduce this problem.

Moving spots in front of the camera at night

This is similar to the spider's web problem but instead of a web, the light is reflecting off dust or particles in the air. This is particularly noticeable in fog where the water droplets suspended in the air reflect the infrared. Warm currents in the air can cause particles to rise as well as fall.

This isn't an exhaustive list of problems encountered at night but it covers the most common ones.

Do you still have any question in your mind?