Digital Noise: What Is It & How to Correct It
Have you seen the term “noise” thrown around and wondered what exactly it is? Or maybe you’ve noticed that some of your images aren’t as crisp and clear as you want them to be, and almost have a grainy appearance to them. Digital noise could be the reason. By understanding what noise is and how it makes its way into your photographs, you can take a few steps to avoid it. And for those times when noise is unavoidable, we will discuss some ways to correct it as well.
What is Noise?
Just like with sound, where noise refers to auditory disruptions, in photography, the term digital noise refers to visual distortion. Noise looks like tiny colored pixels or specks in your photograph, and sometimes resembles the grain that you may see in film photography. You will likely notice noise more in photographs taken in low light situations. Noise can distort the visual detail of your photo, making it something that photographers try to avoid. Several factors can affect the level of noise, including sensor size, higher ISO settings, and long exposures, to name a few.
How to Avoid Noise
If you are noticing a lot of noise in your photos, the first step is to determine what the contributing factor(s) may be. Once you can pinpoint where the noise is coming from, you can take steps to avoid it. These are a few ways you can prevent large amounts of noise:
Lower ISO: Higher ISOs produce more noise, so it helps to shoot with the lowest ISO that you can while still maintaining proper exposure. Different DSLR cameras will vary in their ability to shoot at high ISOs without noise, and this is largely due to the camera’s sensor (more on that below). The examples below show how the ISO impacts the amount of noise in an image. All of these images were shot with a Canon 6D. In the image shot at ISO 16000, the noise is substantially more visible when zooming in on the image. You can see that when the ISO is lowered to even 4000, there is an increase in the clarity of detail and the amount of noise is reduced. This becomes even more evident at ISO 2500.
I try to raise my ISO as a last resort for obtaining proper exposure. When I am shooting in low-light situations and I need to get more light to my camera’s sensor in order to properly expose an image, I will always try to open up my aperture first. If I still need more light, I slow my shutter speed down to the minimum acceptable speed for the subject I am photographing before increasing my ISO.
Larger Sensor: The size of a camera’s sensor plays a large role in the final image quality, including the level of noise in a photograph. Your camera’s sensor contains millions of “photosites,” or light-sensitive spots used to gather and record the information brought in through your camera’s lens. Naturally, a larger sensor has the ability to gather more information. Therefore, the larger your camera’s sensor, the better the image quality. The difference in sensor size is one primary reason why crop-sensor cameras produce images with more noise at increased ISOs than full-frame cameras. You can read more about crop vs. full frame cameras here.
Expose Properly: When a photo is exposed properly, there is less introduction of noise into the image. By getting your exposure right in camera, you can avoid unnecessary noise. See the comparison below. The image on the left was exposed properly in camera, and the image on the right was originally underexposed, with the exposure being increased in Lightroom. Both of the images were shot at ISO 12800. Notice the substantial difference in the amount of noise in the image on the right. Exposing your images properly in camera goes a long way to preventing undesirable noise.
Can Noise be Corrected?
Some cameras have built in noise reduction, which could be helpful, but is not a feature I use since noise reduction is so simple in post-processing. In Lightroom’s Develop Module, you can reduce the appearance of noise in your images by using the Luminance slider in the Details panel. Simply move the slider to the right to reduce noise, using caution to not take it too far. Too much noise reduction can result in loss of detail in your image, giving them a “plastic” look, so be sure to keep an eye on the overall appearance of your image when using this feature.
The next time you’re dealing with digital noise in your images, check to see if one of the tips above can help you to prevent it or correct it, so that you can have crisp, clean images, without the nuisance of the distortion that noise brings to your images.