Photography noise isn't always evident in the photos you take, but when it shows up, it's extremely noticeable.
Similar to grain in analog film, digital noise is usually not something you want, yet sometimes it's also unavoidable.
The question is, what causes noise, and what can you do about it?
Causes of Photography Noise
Noise is essentially random specs that show up in images at the pixel level.
How much noise there is in a photo depends on a number of factors.
First, the smaller the sensor of your camera, the more noise there is likely to be.
For example, since smartphone cameras have very small sensors, their pixels are also smaller, meaning there's a lower signal-to-noise ratio.
In other words, if you photograph the same subject under the same lighting conditions with your smartphone and a Nikon D850, the smartphone photo will have more noise than the one from the Nikon because the Nikon's sensor and pixels are larger.
Another factor that influences how much noise is in a digital photo is the ISO setting.
The higher the ISO, the worse the noise will be.
In looking at the first image in this section, taken at ISO 400 on a Nikon D850 with a 24-70mm f/2.8 lens, you can see that there is very little noise, even when zoomed in.
However, the second image immediately above shows an increase in the level of noise when the ISO is changed to 3200, though it's not an overwhelming amount.
In the shot above, you can see how noise is beginning to become very noticeable at ISO 12,800.
That's because ISO is responsible for determining the sensitivity of the sensor to light. So, when you dial in a higher ISO, it's like turning the volume up on a stereo - the higher or louder it is, the worse the quality will be.
This is true of all cameras, even high-end full frame models like the Nikon D850 that I used to take these photos.
The difference, though, is that high-end cameras can accommodate much higher ISOs with less noise than cheaper cameras can.
Had I taken these images with my iPhone X, we would have seen more noise at a much lower ISO.
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Examining What Noise Looks Like
There are two different kinds of photography noise.
On the one hand, you have color noise (also known as chroma noise), in which there are differences in the colors between pixels.
This looks like a color-speckled effect, and is rarely seen in processed images because color noise is easy to correct in post-processing (and sometimes even in-camera).
In the image above, you can see how even at ISO 20,000, the Nikon D850 does a good job of controlling color noise - there's no visible speckling, even when zoomed in.
On the other hand, you've got luminance noise, which renders as variations in pixel brightness that results in the grainy look you can see in the photo above.
This type of noise is more difficult to handle because, though programs like Photoshop and Lightroom offer luminance noise reduction, using that tool degrades the quality of the image.
In particular, working to eliminate luminance noise results in a loss of fine details and sharpness, with a final image that can look smudged and blurry.
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How to Minimize Photography Noise
Far and away, the most effective method of minimizing photography noise is to keep the ISO setting as low as possible.
Granted, when there's plenty of light - like shooting outdoors during the day or shooting in a studio with a lighting setup - minimizing ISO isn't an issue at all.
The tricky part is when you're in a low-light situation.
To avoid boosting the ISO, you either need to open up the aperture to let more light in or slow down the shutter speed.
When opening the aperture, you run the risk of having a depth of field that's too shallow for the subject, rendering parts of the shot as blurry bokeh that you might not want to be blurred.
Additionally, no lens is its sharpest at its largest aperture, so you also run the risk of capturing images that are less than sharp.
In the case of the shutter speed, at some point it will become too slow to use without a tripod, leading to camera shake.
But even if you use a tripod, if the shutter speed is slow enough, any movement by the subject will be rendered as blurry.
In those situations, you're all but forced to increase the ISO if you want to avoid blurry movement.
The key is to increase the ISO one stop at a time, that way you use the lowest value you can to minimize noise.
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Final Thoughts
In the end, noise can be annoying, but for some photographers, having a noisy photo that's well-exposed is better than having a non-noisy photo that's vastly underexposed.
What's more, noise can be used as an artistic effect, giving your images a gritty, film look. It's especially useful when creating black and white photos.
But, as noted above, if you want less noise, there are a number of things you can do.
Keep the ISO low, open the aperture, slow down the shutter speed, and use a tripod.
You can also process noise out using Photoshop. Learn how to do that in the video above from PHLEARN.