a tool for reducing noise banding
Introduction
All digital cameras produce noise in their images. The higher the sensitivity (ISO) at which the sensor operates, the higher the noise.
Usually, the sensor noise is random, but some sensors create structured noise in the form of bands or color blotches. These blotches are difficult to remove using standard image editing tools.
StripeStripper is a tool for reducing the effect of structured noise. It cannot save every photograph, but it can rescue some photos to the point that noise reduction and post-processing are effective.
How does StripeStripper technology work?
StripeStripper uses three techniques.
Shadow Subtraction Mode
In this mode, StripStripper reduces curves independently in each color channel, but correlates the curve adjustment to overall luminance. If there's blue channel noise in the shadows, StripeStripper can adjust the blue channel curve to suppress the noise only in the shadows. The user selects the luminance level that determines the boundary between shaddow and midtone/highlight.
This method is ideal when the noise is confined to deep shadows.
Shadow Average Mode
Shadow Average Mode computes the average color level given overall luminance level. It then brings up the color in the shadows to match the average. The user selects the luminance level that determines the boundary between shaddow and midtone/highlight.
This method works well in the rare situation in which the image is uniformly dotted with a large number of small shadow areas.
Line Mode
Sometimes, it is easy to identify a region of solid color interrupted by a band of chroma noise. In Line Mode, the user designates a line along which color values ought to change linearly. Deviations from smooth linear color changes along the line are assumed to be indicative of horizontal bands.
This method works very well if there is a flat region with slow color changes and no detail, e.g., uniform, out of focus regions.
StripeStripper is donationware. It is free to download and use for any legal purpose.
If it saves your photograph, or extends your usable ISO, please consider making a donation.
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Copyright 2008 Ivan Phillips.
StripeStripper is a trademark of Ivan Phillips.