Noise Reduction Tab

Noise Reduction is a first step in enhancing the image. All of the following 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 please do not skip this step without good reason.

While on Noise Reduction Tab you can set the zoom level from 25% to 400% by using the thumb wheel on your mouse ().
The less you zoom, the more pixels are processed and the longer at takes the preview to update. The whole image will be processes when you switch on Save or Retouch tab.

Please note that the noise reduction filter is not applied on the tabs where downsized  images are used for faster preview (Brightness, Color, Distortions, Frames tabs). 

To apply all filters and see the final result please switch to the Save tab. If you like the result, you can save it and process the next image. If you don't, you can always switch back to the filter, fine tune the settings and get an updated result.

The program remembers the settings for each file you processed. So when you open the file again, the program recalls the most recent settings for this file. You can also save the file settings manually (Menu->Settings->File Settings).

Controls

The Load settings select box lets you choose one of the predefined settings for this tab. You can also save your current settings for future use.

The Enable noise reduction check-box lets you skip this processing stage completely. If this box is not checked, all other controls on this tab are disabled.

The Noise level, Highlights, Shadows sliders. These three controls define the noise level in the medium, light and dark areas of the image.
Noise level is measured in an abstract absolute value from 0 to 200. You can use this value to compare noise levels in different images.

The program automatically detects the level of noise in highlights, midtones and shadows. If you think the program acts too aggressively, set a lower value of the noise level. If you want to clean a particular area (e.g. sky), use an appropriate slider (Highlights for the sky, Shadows for the dark trees).

Please note, that your settings will be saved automatically and applied to all of the following images. To reset the settings use the Reset  ()button. It sets all sliders to the default (automatically detected) values.

The Radius sets a smooth degree. Higher values result not only in a cleaner image but also in artifacts on edges. Lower values preserve details but also show more noise.

The Chroma defines how strong the noise in chroma channels is if compared to a reduced luminance of a channel.

The Method - select 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.

The Noise Reduction slider defines how much of luminance noise should be removed. In many cases the 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".

The Reset ranges (...) lets you delete all color ranges, which you have added to increase/decrease noise reduction in certain areas. Undo button removes only the last color range. For more details see description of pop up menu commands in the next section.

The Noise Map button lets you switch to a special mode, where intensity of a red color corresponds to the degree of noise reduction. You can use this map to check if fine texture areas are not considered to be noise. It is also a good tool to see effects of the noise reduction equalizer and color ranges.

Pop up menu

Pop up (or local) menu is available by left clicking on the image.

Adjust noise sliders:  The noise level under a cursor will be measured and the appropriate slider (highlights, general noise level or shadows) will be adjusted. You can use small, medium or large area for measurements. Use small area unless you need a very precise noise estimations to compare a noise level of several images.

Increase (Decrease) noise reduction for this color range commands let you change noise reduction for a given (i.e. clicked) color  by 50%. You can use this feature to make noise reduction more selective.
For example, you can increase noise reduction for the sky to clear all noise, and decrease noise reduction for the forest to keep it from smoothing.
Use the Noise Map button to analyze the results more precisely.

The same commands can be accessed through the "Tools" toolbar on the tab. Instead of a right clicking the image and selecting the command you can choose a tool (e.g. "Adjust noise sliders") and then click the image to apply the command.

Please have a look at the example below. The water and trees have almost the same level of details, so the program cannot find where the noise and the texture are. For the image on the right, noise reduction was decreased for the color range of the trees.


Original image
(coastline of a lake)
Denoised image
(the trees are blurred)
Selectively denoised
Noise Reduction Equalizer
To open noise reduction equalizer use appropriate button on the noise tab.

Equalizer lets you define a 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. Sample print screen on the right illustrates this case. Use Noise Map button to analyze the changes more precisely.

To change the equalizer curve simply click on the equalizer at the point that the line is to be raised to and the line will “jump” up to the cursor, then drag left or right to widen the affected color range.

Right Click anywhere on the Equalizer is to reset the line to “straight”.

White vertical line shows you a hue of the area under the mouse cursor. Black line shows the hue under the last click.

Defects and artifacts

The Add or change map files button opens an appropriate tab in the Preferences of the program. There you can define dust/dead pixels maps for every image resolutions.

Please note that sometimes RAW files and JPEG files have difference resolutions. In this case you will need to create maps for RAW and JPEG images separately.

The Filter hot/dead pixels  checkbox makes the program use earlier defined map to mask dead pixels.  This option is available only if you previously defined a map for resolution of the current image. To create the map of dead pixels please close an objective and make a shot. Normally dead pixels will look like bright points on the black background.

The Filter sensor dust  checkbox makes the program use earlier defined map to mask sensor dust.  This option is available only if you previously defined a map for resolution of the current image.

To create dust map please follow through the steps:

1. Set your camera to a manual mode.
2. Set aperture to 8. The dust is practically not noticeable at low apertures (2.8-4)
3. Point your camera at a white sheet of paper or at the sky. The image should not contain dark areas.
4. Unfocus the camera. Otherwise dots on the paper or  birds in the sky will be interpreted by the program as dust points.
5. Make a shot. Repeat for each resolution your usually use. Make a shot in RAW if your RAW files have different resolution from JPEG files.
6. Add dust maps with     button.

Here is an example of the dust map usage (crops, courtesy of Peter Borschberg):
 


Original image
Dust map
 
Filtered image

Tip: you can apply dust filtering to all your images in a batch mode. To do so, please do the following:

1. Reset all using button on the toolbar. All tabs will have gray points on them, which mean that no filter is applied.
2. Go to Noise tab and enable it.
3. Set Noise level slider to 0 to disable noise removal.
4. Set Filter sensor dust checkbox to activate dust filtering. Make sure that you have already loaded dust maps for all image resolutions.
5. Call menu command "Queue/Add current folder"
6. In the appeared Queue dialog set up parameters (folders, formats, quality) and start processing.

Tip for advanced users: you can also save the settings above with a menu command "Settings/File settings" and then apply them to selected images on the Source tab (Right click the image and select  "Apply preset and add to queue" command).

 

Simple mode

If you prefer an easier method – switch to Simple Mode. Click on View, then Simple preview mode. Or Click on the button on the toolbar.

Hints and Tips

Recommended workflow

General workflow

Selective noise reduction.  If you want to change a noise reduction level for specific objects/areas (i.e. skin, sky, green), use Noise reduction equalizer and Color ranges tool.

Using Color ranges:

To show or  hide Help panel of Helicon Filter use button from the toolbar or View->Help panel command in the main menu.