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4 minute read
Reducing Noise in Low Light Images
Noise can spoil a photo made at high ISO settings or with long exposures, but your FUJIFILM camera’s advanced noise reduction algorithms can safeguard against this and protect image quality.
We’ve seen several times in this series how raising ISO sensitivity can help photographers to make images in low-light conditions without resorting to a tripod or flash – rather like turning up the amplification on a microphone when recording a really quiet sound. But unfortunately, this trick doesn’t come for free: as well as amplifying the signal from the camera’s sensor, a high ISO sensitivity can also amplify background electronic noise, which then appears as grain or speckles in pictures.
Digital noise isn’t always a problem – in fact, some film-like grain can add atmosphere to your pictures – but it’s best not to let things get out of hand or image quality will definitely suffer. For this reason, X Series digital cameras apply noise reduction algorithms to images as they are created. The higher the ISO sensitivity, the higher the levels of noise, and the more noise reduction is applied.
You can have some input into this process using the IMAGE QUALITY SETTING > NOISE REDUCTION setting in the camera’s menu system (also accessible in the camera’s Q Menu). Depending on the model you own, you can adjust the amount of noise reduction by up to -4 and +4, with 0 being the default setting.
By turning down the amount of noise reduction applied, you may gain more detail in images, but you’ll also see more noise. Turn up the noise reduction to positive values and you’ll see less noise, but also less fine detail. It’s a delicate balancing act, and one that ultimately comes down to personal taste.
You can also balance the amount of noise reduction applied with the level of sharpening selected (IMAGE QUALITY SETTING > SHARPNESS, or the Q Menu). Again, experimentation is the key.
Noise reduction and sharpening are both saved in custom presets of settings, which can be recalled instantly from the Q Menu.
Note that this in-camera noise reduction only applies to JPEG images. RAW files are created without any noise reduction; this is usually applied in the RAW processing software used to generate the final image.
Long Exposure Noise
Creating images at high ISO sensitivities is not the only time that digital noise can rear its ugly head. When making pictures using very long exposures (such as star trails, traffic trails, and nighttime landscapes) you may also see noise, although it will look different. Instead of the film grain-like appearance of high ISO noise, long-exposure noise is more mottled, and may even show up as bright single pixels of red, blue, or green.
Thankfully, your X Series camera reduces this kind of noise, too. When you photograph at long exposures (more than 1 sec) the camera will make a second, blank exposure straight afterwards with the shutter closed. Since this second exposure contains only the bright noisy pixels, your camera can subtract it from the original exposure to leave you with a cleaner final image.
The disadvantage of this process is that the second blank exposure must be the same length as the first main exposure for the process to work. This can be inconvenient if you’re photographing with, say, 30-second exposures, since you then need to wait an additional 30 seconds to be able to photograph again, during which time you may miss your chance.
For this reason, it’s possible to turn off this behaviour by using the IMAGE QUALITY SETTING > LONG EXPOSURE NR > OFF option in your camera’s menu.
Your Next Steps
- CHALLENGE Experiment with different combinations of noise reduction and sharpening, and save them as custom settings. Post your favourite images to social media with the hashtag #learnwithfujifilm. You can also submit your work here for a chance to be featured on our social media channels.
