Why low light doesn't have to mean high noise – noise reduction features in EOS and Cinema EOS cameras

Image noise is a perennial problem for photographers and videographers when shooting in low light. But don't let the fear of noise hold you back – thanks to the technologies and features now in place in Canon EOS and Cinema EOS cameras, it is more manageable than ever.

Make no mistake: there is random "grain" or visual static in every digital image, but it is more evident if you use high ISO (or gain) settings or a long exposure, because in the shooting conditions where these settings are necessary, there is a poorer ratio of image information to noise. Turning up the ISO amplifies both the information and the noise, making the noise more apparent. In the same way, recovering shadow detail in post-production seems to introduce noise, but actually it is just making visible the noise that has always been present in the image – the shadows are areas where by definition less light has reached the sensor and there is consequently less image data in proportion to noise.

So is it possible to minimise or even reduce noise in images and video shot in low light? Here's a quick guide to noise reduction technologies and options, particularly those available in-camera in Canon cameras.

"There are essentially two categories of noise," says Mike Burnhill, Senior Product Specialist at Canon Europe. "First, there's the category of noise which is created at the pre-capture stage by inherent electromagnetic phenomena – things like photon shot noise or crosstalk. At Canon, we're always trying to reduce this type of noise by redesigning sensors to help improve the signal-to-noise ratio.

"Then there's the category of noise that's generated at the digital image processing stage, which can be broken down into chrominance noise and luminance noise." These two types of noise can be tackled with noise reduction, which can be applied either in-camera or using software. Noise reduction capabilities in current Canon EOS and Cinema EOS cameras are more sophisticated than they've ever been. And the processing horsepower that you get with a computer and software such as Canon's free Digital Photo Professional (DPP) enables further noise reduction results.

The latest EOS cameras such as the Canon EOS R5 and EOS R6 feature three types of built-in automated noise reduction: High ISO Speed, Multi-Shot and Long Exposure.

Despite the name, High ISO Speed noise reduction can be applied at all ISO settings – although its effects are more noticeable at higher ISOs. "Each camera has chrominance and luminance patterns mapped out in the system," Mike explains. "These presets, designed by our engineers, are based on the sensor specification and ISO settings. They basically tell the camera that when a JPEG is shot at a certain ISO, a specific noise reduction value needs to be applied."

You can set the overall strength of High ISO Speed noise reduction at three levels, but you can't fine-tune the chrominance and luminance settings in the same way that you can in software such as DPP. "The presets need to be pre-mapped for speed," says Mike. "When you're shooting a football game at 30fps with the Canon EOS R3, for example, then you have to have a hard-wired setting that means the whole process is instantaneous."

Like High ISO Speed noise reduction, Multi-Shot noise reduction can be applied only to JPEGs in-camera. "It's a technique that could work with RAW files, but again, it's all about making the whole process easier and quicker," says Mike.

"Multi-Shot noise reduction is a similar process to focus stacking, as it requires multiple images taken from the same position to be stacked and compared. The camera is then able to remove the random noise by keeping only the data that is in the same place in every frame.

"This is the reason why this type of noise reduction is really designed only for stationary objects. Anything that moves between the frames could be seen as noise and get mapped out."

Shooting video can also generate relatively high heat levels, and noise in a moving image is much harder to deal with. "Some EOS cameras let you shoot RAW video so you are able to do a lot more processing later on," says Mike. "But it is difficult to edit video because you have so many frames. Therefore it makes sense to use as low an ISO as possible and then use noise reduction in-camera to try to reduce it at source."

Aron Randhawa, Pro Video Marketing Specialist at Canon Europe, agrees that in-camera noise reduction is an essential aspect of video production. "Video camera operators have less flexibility to control exposure through shutter speed, and noise patterns can become more noticeable in images when they move. In addition to this, it's now become essential for video cameras to minimise noise in order to provide the extended dynamic range expected for HDR content delivery."

"Our video cameras also feature DIGIC DV processors that use sophisticated software algorithms to reduce noise while maintaining high image quality," Aron continues. "This processing can be completely controlled by the user in the Cinema EOS range, via the Spatial Filter and Frame Correlation noise reduction controls. The Spatial Filter applies a small soft-focus-like effect to the image, while Frame Correlation compares the noise level between different frames and then uses that information to reduce it."

The latest Cinema EOS cameras offer 1-12 levels of noise reduction using the Spatial Filter control and 1-3 levels of Frame Correlation. The default setting for the Spatial Filter varies between cameras. On the Canon EOS C500 Mark II, for example, it's set to level 1, but on the EOS C300 Mark III and the EOS C70 it's set to off. "That speaks volumes about how good the DGO sensor is at controlling noise," says Aron. "And of course no noise reduction is applied to any footage when captured in RAW. That's so users have greater control of the fidelity in post.

"Frame Correlation is always set to off by default across the Cinema EOS range. One of the reasons we don't enable it is because of the potential variation in performance between different scenes. There may be some scenes where the Frame Correlation is working fairly heavily because it can really pick up the noise between different frames, whereas in others it may not pick up the subtle noise as much."

As well as applying noise reduction, there are ways to minimise the risk of noise in video footage. "One of the fundamental elements of achieving high-quality imagery in both videos and photos is actually having a strong signal-to-noise ratio," Aron explains. "One of the first things you can do to strengthen that ratio is to light your scene appropriately. Add more lights before you start thinking about amplifying the image in the camera with a higher ISO or gain.

"Your next step is to open the aperture to get more light into your camera. Also, think about the shutter speed: would you find it acceptable to go to 1/25 sec or do you need to stick with 1/50 sec? Finally, consider switching your Log Gamma Curve from Canon Log 2 to Canon Log 3 if you want to try to ensure the shadows are a bit cleaner.

"Once you've exhausted all of these options, that's when you can start to push the ISO."

Combining such strategies with the advanced technologies in Canon's current cameras – including breakthrough sensors and image processors designed for an improved signal-to-noise ratio, and powerful in-camera noise reduction – means you can shoot cleaner images and video even in low light.