Types of Noise

There are three primary types of noise that occur in digital images:

Luminance noise

Luminance noise is like film grain, to which it is often compared. It’s evenly distributed across an image and is usually the result of using a high ISO. With most pre-2011 camera models that would be ISO 800 or higher. With most newer cameras that would be ISO 1600 or higher, and many are able to do better than that. However, this is just a general rule and needs to be tested by photographing in low-light and progressively increasing the ISO. Be certain to use a tripod so that other factors, such as normal body tremors, don’t influence the results.

Color Noise (chrominance)

Color noise appears on the screen or in the print as small red, green, or blue dots and is mostly seen in shadow areas. Long exposures, more than one or two seconds, will often greatly increase the incidence of color noise, as will gross underexposure.

Both luminance and color noise can be controlled in the camera by using wider aperture lenses such as f/1.4, f/1.8, f/2.8, for shorter exposure times, and a lower ISO whenever possible.

Hot Pixels

Hot pixels appear as white pinholes in an image. There are several causes, but the most common is heat generated by the rapid movement of electrons across the sensor, which often happens with sustained, high speed recording. The second most common cause is ambient heat from physical surroundings. This can happen just by leaving the camera in the front seat of your car or in the trunk on a sweltering day.

There is a simple algorithm used by many camera makers that recognizes hot pixels and replaces them with the most likely color, based on an average of its nearest neighbor pixels. As a result, hot pixels are not as common as they once were.

Reducing Noise

Noise is most commonly encountered in low-light photography, high ISO captures, long exposures, or underexposed images. Here are common strategies for noise reduction.

Exposure Management: To maximize image quality and minimize noise, use the lowest possible ISO settings for your desired exposure. Using faster lenses (e.g., f/1.4–f/2.8), shorter shutter speeds, and the lowest viable ISO setting helps reduce noise during capture.

In-Camera Noise Reduction: Most digital cameras include settings to reduce noise either during high ISO shooting or long exposures. These features often involve additional processing time and may delay the next shutter release.

Post-Processing Software: Noise reduction tools are integrated into most photo editing software. Applications such as Adobe Lightroom and On1 PhotoRAW offer adjustable sliders for targeting luminance and chrominance noise independently. Third-party plugins—like Imagenomic Noiseware, Skylum Denoise, and DxO’s Dfine (part of the Nik Collection)—provide advanced noise reduction capabilities, often tailored to specific camera profiles.

In some cases, aesthetic techniques are used to mask noise. For example, adding a uniform film grain pattern can create visual consistency across an image, making luminance noise less noticeable. Similarly, converting color images to black and white can help eliminate visible chrominance noise.

Is Even Bad Noise Bad?

Not all images require noise reduction. In some cases, noise can be intentionally used as a creative element to convey a sense of authenticity, texture, or a nostalgic, film-like aesthetic. This approach is common in genres such as photojournalism, documentary work, and certain styles of wedding or street photography. However, in contexts where technical accuracy is critical—such as product photography, astrophotography, or large-format printing—noise is generally considered undesirable and is carefully minimized or removed through in-camera settings and post-processing techniques.