Need to reduce noise / but not detail

Started 2 months ago | Discussions thread
The Ghost of Caravaggio Contributing Member • Posts: 770
There Are No Miracles

This image seems to be over-sharpened and actually doesn't have a noise problem.

However, noise reduction algorithms can not increase an image's information content .[1] To some extent detail is always compromised by noise reduction algorithms.

Noise reduction is essentially a mathematical filtering process. At the risk of over simplification, regions with high noise are cleverly averaged with nearby regions with less noise. The result is a compromise. The perceived quality of noisy regions improves at the expense of the information content in less noisy regions. The image's total information content remains constant.

Often this compromise is worthwhile. The perceived decrease in noise can be more noticeable than the decrease in detail. When the loss of detail is acceptable, the perceived image quality increases.

1. Temporal noise reduction for still photography is relatively unsophisticated. For instance, when significant prior information is available, maximum use of image information content is possible. Loss of detail can be great reduced. However the image information remains constant. The difference is objective information from other sources is applied to the problem.

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"The belief that ‘randomness’ is some kind of real property existing in Nature is a form of the mind projection fallacy which says, in effect, ‘I don’t know the detailed causes – therefore – Nature does not know them."
E.T Jaynes, Probability Theory: The Logic of Science

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