Digital cameras or scanners often produce images that contains noise,
especially when using high ISO. This noise is made of random pixel
variations that damage the picture in different manner, adding unwanted
granular effects. To obtain a good result, this noise should be removed
paying a great attention to :
- Image details that often can be removed with noise, and edges definition that are often blured by basic noise reduction technics.
- Keeping some granularity to avoid the common "plastic" effect of too much noise removal.
AbsoluteDeNoiser (Free version) works in 3 steps :
- Edges detection: this analyse makes a separation between large surfaces with poor
details, and places where some edges and/or details require a special attention. The value to tune enables to decide the sensitivity of the edges detection, thus the amount of the picture that is to be considered as details/edges or not. Surfaces and edges will then be
processed in different ways in next steps.
- Surfacing: performs a calculation of local color cohesion to decide, for each
pixel, what is the mean color value in the noise variations arround it, without merging
two different surfaces together. This step also processes surfaces and edges in two
different ways. The more important is the value that tunes the surface
managment : it is the one that decides of the effective noise
reduction. There is also a secondary value that tunes the edges
managment, but it should often be kept at a low value to avoid bluring
edges : in some cases it offers the possibility to reduce some edges
pixelisation effects.
- Texturing: the step 2 may provide with "too" clean surfaces where some small details or textures could have been lost, and possibly a "plastic" effect. This final filter decides the
amount of original pixels that should be added back to the clean surface
to restore details and textures without re-introducing the noise that
should be removed. A first value tunes how much part of pixels that was removed in step 2 shows a local regularity, thus how much noise vs details is to be
considered on them. There is also a secondary value that tunes how much
pure granularity, without special regularity, should be added back
without re-introducing bad strong spots and scratches.
ScreenShot
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