Night vision and low light: what to check before you buy a CCTV camera

Ask people when they most need their CCTV footage and they will say after closing, in the night, when nobody was there. Ask how the cameras perform in the dark and many will not know, because nobody checked.

This is the most common disappointment with CCTV. The camera looked sharp in the shop demonstration under bright lights. Then something happened at two in the morning and the footage shows a grey smear and a pair of glowing eyes.

Night performance is not a single number on a box. It is a result of several things working together, and each can be checked before you buy. This guide explains them, so that you can choose by what the camera will record in the dark, not by what the brochure promises.

For choosing cameras in general, including resolution and lens, see choosing CCTV cameras. This post goes deeper on the dark.

Why night is hard for a camera

A camera makes a picture by collecting light. In daylight there is plenty. At night there is very little, and the camera has to work with whatever it can gather.

Two things happen. The camera slows its shutter to collect more light, so anything moving is blurred. And it amplifies the signal, which also amplifies noise, the speckled grain you see in dim footage.

So the real question about a night camera is how well it manages with little light, and how much light you can supply for it.

Sensor size and pixel size

The sensor is the chip that catches light. A larger sensor, or larger pixels on it, catches more light and produces a cleaner picture in the dark.

This is where marketing misleads. Two cameras can both claim 4 megapixels, but if one has a larger sensor, each pixel is bigger and gathers more light. The other crams the same number of pixels into a smaller area, so each one is tiny and noisy.

What this means in practice:

Higher resolution is not better at night. An 8 MP camera with a small sensor can look worse in the dark than a 2 MP camera with a good one.
Look for the sensor size. Specifications often list it as a fraction of an inch, such as 1/2.8”. A larger fraction, such as 1/1.8”, is a bigger sensor.
Look for low-light claims with a number. A rating in lux, such as 0.005 lux colour, tells you the minimum light at which the camera still produces a usable picture. Lower is better, though manufacturers test under their own conditions.

Lens aperture

The lens controls how much light reaches the sensor. A lens with a wider opening, written as an f-number such as f/1.6, lets in more light than one at f/2.8. A smaller f-number is brighter.

A fast lens is one of the cheapest improvements to night footage, and many buyers never look at it. Check it in the specification, next to the focal length.

Infrared, and how far it really reaches

Most cameras handle darkness with infrared (IR). Small LEDs around the lens light the scene with a wavelength people cannot see, and the camera records in black and white.

A few things to know.

The stated range is optimistic. A “50 metre” figure is measured in ideal conditions, in an open space with a reflective target. In a real yard with dark ground and walls, expect less, often half.
More is not better. A camera pointing at a short corridor with very strong IR will wash out anything near the lens. Match the range to the distance you actually need to cover.
IR bounces. Glass, polished walls, wet surfaces and rain reflect IR back into the lens. A camera behind a window sees a glowing white pane and nothing else. Mount it outside the glass, or use a camera with a white light instead.
Spiders and insects. Cobwebs near the lens, lit by IR, fill the image with bright flashes. Position cameras away from them and clean regularly.
Dome covers. A plastic dome can bounce IR back inside the camera. Turret and bullet cameras avoid this, which is why they are common choices for night coverage.

Colour at night

An IR image is black and white. That helps you see that someone is there, but not what they were wearing or what colour the vehicle was, which is often exactly what an investigation needs.

There are two approaches.

Colour night vision. A bright lens and large sensor record colour in very low light. It needs some ambient light, such as a street lamp or a lit shopfront, and shows clothing and vehicle colours.
Hybrid white light. The camera records in IR normally and switches on a small white lamp when it detects a person. It gives true colour exactly when it matters, and a visible lamp can deter someone before they act.

Which is better depends on the place. A dark yard behind a shop suits IR. A front door with a street lamp nearby suits colour. An entrance where you want a deterrent suits a white light. Many sites use a mix.

WDR and bright lights in the dark

Night scenes often contain one very bright thing in the dark: a headlight, a street lamp or a lit doorway. The camera has to expose for both at once.

WDR (wide dynamic range) combines several exposures so that dark and bright areas are both readable. Without it, a face in front of a headlight becomes a dark silhouette against a white glare. For gates, doorways and anywhere cars come in, WDR is worth looking for. Check that it works at night, not only in the daytime.

Shutter and motion blur

At night, the camera lengthens its exposure. A person walking through the frame is then blurred, and a face cannot be read.

Many cameras let you set a maximum shutter time. A shorter shutter reduces blur but makes the picture darker and noisier. Providing more light, rather than relying on the camera to make do, lets a shorter shutter be used and gives sharper results.

Add light, not only a better camera

A better camera helps. A lamp helps more. A modest, steady light at a door or gate can lift footage in a way no sensor upgrade will.

Light the area you care about, not the whole yard. A lit doorway and path are more useful than a bright but unfocused wash.
Avoid pointing lights into the lens. Glare ruins the picture. Place lamps beside or above the camera, aimed at the scene.
Keep it steady. Flickering or motion-triggered lights confuse exposure. A constant, low-level light works better.
Check the colour. Warm and neutral white lights give more natural colours than harsh blue ones.

How to test before you commit

Never judge a night camera by its brochure or by a daytime demonstration.

Ask for it at night. Test the camera at the real location, in the evening, before you buy many.
Walk the scene. Have someone walk through at the distances you care about, and check you can read a face or a plate.
Pause the footage. Moving video forgives a lot. Stop on a frame and see if it is usable.
Check the compression. Heavy compression smears detail in dark areas. Look at the actual recorded footage, not the live preview.
Look at the worst corner. The darkest, farthest spot is where the camera will be asked to perform.

An installer who is confident in their equipment will welcome the test.

Common mistakes

Buying on megapixels and ignoring the sensor and lens.
Trusting the IR range on the box.
Mounting cameras behind glass.
Pointing a camera directly at a street lamp or headlights with no WDR.
Judging only by daytime footage.
Leaving spiders’ webs near the lens.
Assuming a camera that works at the front also works in the darkest corner at the back.

The short version

A camera records what the light lets it. At night there is little, so the result depends on sensor size, lens aperture, IR or white light, WDR, and how much light you supply yourself. Check each, test at the real site in the real dark, and choose the camera that records usable footage in your worst spot, not the best one on the box.

Questions people ask

Is a bigger IR range always better?

No. IR range is measured in ideal conditions. A camera that covers a 10 metre area does not need 50 metres of IR, and too much IR close to a wall or a glass door washes the picture out.

Why is my night footage grainy even with a good camera?

Grain is noise from a sensor working in low light. It is made worse by small sensors, high resolution on a small sensor and heavy compression. More light on the scene helps more than a new camera.

Should I choose colour night vision or infrared?

Colour night vision shows clothing and vehicle colours when there is some light or a white lamp. Infrared works in total darkness but is black and white. Many entrances use a hybrid of both.