ARTICLE

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

You don't need to fear unacceptable levels of noise when shooting in low light. Canon experts explain the noise reduction technologies and options in the latest Canon EOS and Cinema EOS cameras.

A man faces sideways, holding a camera to his face, silhouetted against a purple and orange sky at sunset.

Shooting at a high ISO in low light is a recipe for image noise. In many situations, however, the stability delivered by the combination of an image-stabilised lens and in-body IS in the Canon EOS R5 means that you can avoid pushing the ISO too high. "In the old days, the solution was often a tripod," says Canon Europe's Mike Burnhill. "But tripods aren't always practical. So the ability to shoot handheld using a slower shutter speed at a lower ISO opens up a whole range of possibilities."

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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.

A low-light shot of a landscape looking over a body of water towards steep hills. The right-hand half, taken at high ISO, displays markedly more noise.

Noise is a familiar problem in high-ISO images. The left half of this image was shot at ISO100 with a 2.6 sec shutter speed, but the long exposure has meant that the moving water is blurred. The right half was shot at 1/125 sec – but in order to let in enough light at this shutter speed, the ISO was increased to 25,600. This has captured much more detail of the water surface, but the image noise is significantly worse – it's especially noticeable in the sky. Both shots were taken on a Canon EOS 850D with a Canon EF 16-35mm f/2.8L II USM lens (now succeeded by the EF 16-35mm f/2.8L III USM) at 23mm and f/8.

A Canon EOS R6 camera with no lens attached, so that the full-frame sensor is visible.

A higher signal-to-noise ratio will produce cleaner images, the "signal" being the image information captured by the camera. "Fundamentally it comes down to pixel size – the actual photo-receptors or 'light wells' on the sensor," says Mike. "In a like-for-like sensor, the larger the light well, the more photons it can absorb, so therefore the better signal-to-noise ratio it has." This is a key reason for the outstanding low-light performance of the Canon EOS R6: its 20.1MP full-frame sensor has fewer pixels spread across the sensor area than a 45MP full-frame sensor, for example, which means they are larger.

Using in-camera noise reduction

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."

A screenshot of Digital Photo Professional showing a tree silhouetted against a purple sky, with noise reduction controls to the right.

The noise reduction options in Canon's Digital Photo Professional software let you tackle the chrominance (colour) noise separately from luminance (brightness) noise, and will be useful no matter what camera you have used. "If you're shooting with a high-resolution camera, then you might want to apply a bit more luminance noise reduction because you could take the hit in resolution," suggests Mike. "But when you have a lower resolution camera, reducing the luminance noise can mean you lose more detail."

A cutaway illustration of a Canon EOS R3 camera, showing the RF lens mount and the camera sensor.

The Canon EOS R3's back-illuminated sensor design allows more of the processor circuitry to be brought into the sensor itself. "Being able to move the A/D converters closer to the signal means that there's less chance of interference getting into the way and generating more noise before you actually convert it into a digital processed signal," explains Mike.

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."

Long Exposure noise reduction can be used for both JPEGs and RAW files. It requires a second exposure to be made in-camera in order to map out the fixed-pattern noise generated during a long exposure. "The process is essentially a modern version of dark frame subtraction," Mike explains. "That requires two pictures to be taken one after the other, but with the lens cap on for one of those shots. In the case of current EOS cameras, though, the shutter is automatically closed for the second exposure." With no light reaching the sensor, this shot will contain only a noise pattern.

"The camera compares the noise on the dark frame with the image so it can map out any stuck pixels or noise that's generated randomly by the system rather than the camera."

The heat produced by the camera during a long exposure is a potential source of interference, and Mike advises letting the camera cool off a bit between shots. "A simple thing like folding out the screen can help the camera stay that bit cooler," he adds.

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A view looking up through the fronds of tall palm trees to the night sky filled with stars and the Milky Way.

Astrophotography is one area where you need to shoot with a relatively low ISO and minimise noise at the image capture stage. "You don't want to over-process noise in an astro shot, because that can actually take out stars," says Mike. Taken on a Canon EOS R6 with a Canon RF 16mm F2.8 STM lens at 25 sec, f/2.8 and ISO6400.

A close-up image of flowers in a field, with a histogram strongly skewed towards the right-hand (highlights) end.

In stills, using the ETTR (exposing to the right) technique can help to minimise noise in darker areas of a RAW file shot in daylight. The process requires the shadows to be overexposed in-camera, so that these areas contain as little noise as possible, and the exposure is subsequently corrected in RAW processing software such as Canon's Digital Photo Professional (DPP).

Reducing noise in video

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."

A diagram of the concept of Canon's DGO sensor technology: a high-gain readout is combined with a lower-gain readout to produce a single HDR image.

In Canon's DGO (Dual Gain Output) sensor technology, built into the EOS C300 Mark III and EOS C70 professional video cameras, each pixel on the sensor is read at two amplification levels, and the two readouts are then combined into a single image. The higher amplification signal captures subtle details in the shadows and reduces noise, while the lower amplification optimises information in the highlights. Combining the two produces stunning, clean HDR footage.

"Noise reduction in our Cinema EOS cameras works hand in hand with both hardware and software," Aron says. "In terms of the hardware, Canon has continuously developed cutting-edge image sensor technology to ensure light is captured with minimal noise.

"Since the launch of the original Canon EOS C300, we've utilised the innovative design of Dual Pixel CMOS technology to help to reduce noise levels. This is done by capturing light with two separate photodiodes per pixel, which allows the sensor to normalise those readings and therefore reduce any potential noise."

Canon's video sensor technology has continued to evolve, with the Canon EOS C300 Mark III and EOS C70 both featuring Canon's revolutionary Dual Gain Output (DGO) sensor. "This produces two images that are read at different amplification levels and then merged to produce an image with low noise and 16 stops of dynamic range," explains Aron.

DoP Ben Sherlock filming with the Canon EOS C300 Mark III in a rural setting with bushes and water in the background.

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A close-up of the LCD screen of a Canon EOS C70 showing two people being filmed and the settings used.

With Cinema EOS cameras, you have the option to shoot in Canon Log 2 or Canon Log 3 – the display confirms that the latter is in use here on a Canon EOS C70. "Canon Log 2 provides the greatest dynamic range, but it can also increase the noise levels in the shadows," explains Aron. "Canon Log 3 requires less treatment to the image in post production. However, thanks to the benefits of the Canon's new DGO sensor, Canon Log 2 is becoming more accessible to everyone – even those who want a quick turnaround with less post-production time."

Cinema EOS noise reduction options

"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."

A cinematographer films with a Canon EOS C300 Mark III in a junkyard strewn with debris.

"If you go to the higher end of the Spatial Filter – from 1 all the way up to 12 – on a Cinema EOS camera, the biggest disadvantage is that the image is going to become significantly softer," says Aron. "This may be a problem if you're on a high-end cinema production, but if you're a documentary filmmaker shooting for television then it may be more acceptable." © Ron Batzdorff

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.