Tabs - Noise Reduction / Sharpening
This tab contains the settings of two filters:
- Noise Reduction - this filter reduces the color and brightness noise and the dot matrix in scanned typographic images;
- Sharpening - the filter for increasing the image sharpness.
An example of removing the dot matrix and increasing the sharpness (the image is enlarged two times):
|
|
|
Source image (scanned)
|
Noise Reduction
|
|
|
|
|
Noise Reduction + Sharpening
|
Noise reduction and sharpening the image are relatively slow operations so there is a preview area for you to be able to preview the result in real time. This area is always located in the center of the screen. Just drag the image to move the necessary image part to the preview area. By default, the borders of the preview area are visible while you are dragging the image. You can change the preview area options in View > Options... > UI Settings > Noise Reduction.
|
|
Source image (you can see the filtering result in the Preview Area)
|
Noise Reduction
Allows you to reduce or nearly completely remove noises from the image. For example, noises in digital photos when you take them with little light that even get larger when you increase the exposure, brightness, etc.
To use this filter, you should:
- Select a noise sample - a small area in the image that contains noise, but does not include any important image details;
- Adjust the level of noise reduction using the Chrominance, Luminance and Blending sliders.
To select a noise sample, click the "Select Noise Sample" button (  ) and use the mouse pointer to select the necessary image part by pressing and holding down the left mouse button while moving the mouse. If the selected part is too small, it will be automatically enlarged to the minimum required size.
Examples of "good" and "bad" noise samples:
The filter parameters are adjusted with the following sliders:
- Chrominance - color noise reduction level;
- Luminance - brightness noise reduction level;
- Blending - adjusts the level of blending between the filtered and original image.
If a file in the JPEG format is loaded and the image has compression artifacts in the form of visible squares, it is recommended to use the Suppress JPEG artifacts option.
Sharpening
Low image sharpness can be the result of low-quality shooting, or applying the noise filter, or reducing the image size. This filter helps you reduce this defect - sharpen the image.
The filter parameters are adjusted with the following sliders:
- Amount - the level of sharpening the image;
- Radius - the size of the detail contour zone where the sharpness will be increased. The following rule is usually true: the larger the image size is (in pixels), the greater this parameter (Radius) should be;
- Threshold - the filter sensitivity threshold. The larger this parameter is, the lower the filter sensitivity to noise is.
If you set Amount and Radius to large values, the halo effect appears on the borders of contrasting details. To reduce this effect, you should enable the Suppress halos option.
Example:
|
|
|
|
Source image
|
Halo effect
|
Suppressed halos
|
|
