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If you’ve ever set your ISO toward the higher end of your camera’s range, you will find that your photos don’t always turn out so great. Digital noise is generally noticeable in photos that have been taken with a high ISO setting. Managing digital noise is important when you move toward the limits of your camera’s ISO range.
In this article, we’ll take a look at various techniques, both in-camera and during post-processing, for managing digital noise.
Noise varies from camera to camera depending on the quality of the sensor. You’ll have noticed it in photos made with your smartphone at night. When the light is low and the ISO is high, a phone or camera with a very small sensor is prone to producing a lot of digital noise. On higher-end full-frame cameras there’s not so much of an issue with digital noise until your ISO reaches the highest settings it’s capable of.
At first glance, digital noise may not be so noticeable. But when you enlarge an image made using a high ISO, it is easy to see noise speckles. These speckles are discolored pixels and pixels with an incorrect luminance value. They contrast with the surroundings in an unnatural way.
Digital noise in photos is not the same as grain. Grain is associated with film and has a different appearance than digital noise. Different types of film have different grain structures. Grain can be used to creatively enhance photos, whereas digital noise degrades an image.
There are two types of digital noise that affect your photos when you use a high ISO setting. These are color noise and luminance noise.
Color noise, or chromatic noise, appears as discolored pixels that contrast with how the colors in a photo should look. It’s most apparent in the very light or very dark areas of photos taken at high ISO settings. Sometimes this type of noise is difficult to eradicate. The best approach can be to simply convert your photo to black and white.
Luminance noise shows up as pixels that are brighter than they should be. When you raise the ISO setting on your camera, the pixels on the sensor become amplified and distort. Think of it as like turning the volume on your stereo up too high to the point that the sound distorts.
The most surefire way to avoid digital noise is to keep your ISO setting low. This is not always possible, especially when photographing in low light conditions.
Raising your ISO increases the risk of adding unsightly noise, but it also allows you to choose a narrower aperture and faster shutter speed.
Getting sharp photos of action at night requires a fast shutter speed. And an easy way to achieve this is by raising your ISO setting. So it’s not always possible to avoid noise. Managing digital noise when you post-process your photos then becomes necessary. There are various tricks and tools you can use to do this.
Try this exercise to discover the highest ISO setting you are comfortable using on your camera:
Find a reasonably dark place to take photos of a static subject, such as a room with the drapes drawn or outside at night. Set your camera on a tripod, or on a firm surface where it won’t move.
You can set your camera to any exposure mode you’re comfortable with, but you must set your ISO to manual. And if you use your camera’s manual exposure setting, balance your aperture or shutter speed before each shot (so your meter is always reading zero).
Start with the lowest ISO setting. This is usually ISO 100. Take a photo of your subject. Then change your ISO setting to 200. Take another photo.
Repeat this process, doubling the ISO, until you have taken a series of images throughout the ISO range.
Study the photos on your computer. Zoom in to 100% and look at the digital noise. At what ISO setting does the digital noise appear to degrade image quality? The ISO setting below that point should be the maximum you use.
Post-processing programs and apps have functions that can reduce digital noise in photos.
The less noise apparent in a photo, the more successfully you can remove it. If you’re too aggressive with managing digital noise, your photos will appear soft and blurry.
In the Develop module in Lightroom, click on the Details Panel on the right side of the screen. Here you’ll see a number of sliders. The ones you want to use are the Luminance and Color sliders.
Start with Luminance slider and drag it to the right. Then slide the Color slider if you still see some noise. Watch what’s happening to your image as you do this. You don’t want to slide it further than you need to. The further to the right you move these controls, the softer your image becomes.
The amount you need to adjust the sliders will vary from image to image.
If you prefer using Photoshop, you’ll still find good controls for managing digital noise.
In the top menu select Filter>Camera Raw Filter. In the new window that opens, select the Details icon (it’s the two triangles). Here you have the same two sliders as in Lightroom: Luminance and Color. Slide them to the right only enough to get a satisfactory result.
You can further reduce noise by selecting Filter>Noise>Reduce Noise from the top menu.
Photoshop allows you more flexibility in reducing noise. You can isolate the problem areas with masks or multiple layers. This can help retain detail in important areas of your compositions.
When you are photographing a static subject and have your camera on a tripod, take two or more photos.
Open two of the photos in separate layers of the same file in Photoshop. Once you’ve done this, the easiest way to reduce the noise and retain clarity is by changing the blend mode of the top layer. The Multiply blend mode usually works well. You can also experiment with Overlay and Soft Light blend modes.
Whenever I’m taking photos, I try to maintain the lowest ISO setting possible to avoid digital noise. In many low light situations, using a higher ISO setting is necessary to take photos without extra lights.
Each camera model manages digital noise differently. Use the experiment I outlined in this article to ascertain the highest ISO setting at which you are comfortable shooting.
Managing digital noise is now easier than ever. Cameras have more advanced sensors than early digital cameras had. And imaging software has also evolved to be better at managing digital noise.