Removing noise

When you switch to the Noise filter the program automatically detects the level of noise for your image and corrects it. In most cases this will be enough. But sometimes it is necessary to reduce noise more intensively for some parts. The Hightlights and Shadows sliders and the Equalizer allow reducing noise more intensively only for particular areas of the image - for highlights, for shadows, or for specific colors. These tools are described below.

noisy image noise removed
Noisy image Noise removed

The noise reduction is similar to blurring and it can result in loosing details. So, you need to find the reasonable balance between the details level and the noise level for your particular image.

You can change the parameters of the noise reduction algorithm in order to get better results for your particular image. This makes sense because different images have different noise and detail levels.

Hints and Tips

Noise reduction is an important step in enhancing images. All the other operations like sharpening and color balancing increase noise and make it more noticeable. It is important to clean the noise from the image at the very beginning. Even bright images shot on a sunny day contain a lot of noise so do not skip this step without a good reason.

  • Noise looks worse on a monitor screen than it does when printed.
  • Noise is noticeable on homogeneous areas (i.e. sky), and is hardly visible on textures (i.e. foliage).
  • Images with too much noise reduction look unnatural (plastic).
  • Do not spend too much time on a fine tuning - nobody will notice the marginal improvements.

Noise Level

The Noise level slider defines the level of noise reduction for the whole image. The default noise level is detected automatically after you switch to this tab. Noise level is measured in an abstract absolute value from 0 to 200. You can use this value to compare noise levels of different images.

Shadows

The Shadows slider defines the noise reduction level in shadows. If set to 0, it means that the noise reduction level in shadows is the same as in highlights and in midtones. If set to -100%, it means that there is no noise correction in shadows. If set to +100%, it means that the noise reduction level in shadows is twice more intensive (200%) than on the rest of the image.

Highlights

It works the same way as the Shadows slider, but for the highlights.

Noise Reduction Equalizer

The equalizer lets you define the noise reduction level for every hue in your image. Usually higher noise reduction levels are set for skin tones and the sky with lower levels set for green.

original with noise noise reduced everywhere denoised equalizer
Original noisy image Noise reduced on the whole image Noise reduced only for blue colors The Equalizer settings

Use the Noise Map to analyze the changes more precisely.

Algorithm parameters

Radius - higher values result not only in a cleaner image but also in artifacts on edges. Lower values preserve details but also show more noise.

Chroma - defines how much of chromatic noise should be removed. Chromatic noise shows up as points coloured in a complete different way they should be.

Noise reduction - defines how much of the luminance noise should be removed. In many cases an image looks more natural if chroma noise is completely removed, but a part of the luminance noise is left. Completely denoised image may look too "plastic".

Method allows selecting an algorithm which gives the best results on your particular image. For images with low noise, the "standard" method is good enough, for very noisy images try the"aggressive" method. These methods use completely different algorithms.

Noise Map

On the noise map you can see the noise reduction level for different areas of the image. The intensity of the red corresponds to the noise reduction level. You can use this map to check if fine textured areas are not considered to be noisy. It is also a good tool to see the effects of the noise reduction equalizer and the highlights/shadows sliders.

Selection Brush

selection brush The selection brush selects some area of an image. After you have some selection you can return to the Noise filter and apply any transformation either only to the selection or only to the rest of the image. Learn more about selection brush and it's parameters here.

Noise Reduction Brush

noise reduction brush The noise reduction brush allows reducing noise only for some parts of the image. For example, you can reduce noise only for faces. Learn more here.