contrast & texture
Technical information
- description
- enhance local contrast by boosting details while preserving edges.
- purpose
- creative.
- input
- linear, RGB, scene-referred.
- processing
- linear, RGB.
- output
- linear, RGB, scene-referred.
contrast & texture is the scene-referred counterpart to the display-referred local contrast module. It can be used for both adding punch to, for example, clouds or foliage and for smoothing busy areas (like softening skin or calming down a cluttered background). It can also be used to manage highlights and shadows as the scene referred equivalent of the display referred shadows and highlights.
The module uses the same exposure-independent guided filter (eigf) used by the tone equalizer module for its guided mask. The affected scale of detail can be tuned with the module’s controls, and three separate scale levels can be targeted individually. The underlying filter is exposure-independent, so the strength of the effect stays consistent across shadows and highlights alike.
A noise bias control lets you tame the amplification of shadow noise, which would otherwise be boosted along with genuine detail since both look like local contrast to the algorithm.
To build up a more elaborate effect, multiple instances of contrast & texture can be used together, each targeting different detail scales and possibly masked to different parts of the image.
Multiple controls have a mask display button
available - only one mask can be displayed at a time, so clicking on a mask display button turns off any other mask currently being displayed.
Note: This module is a first step towards a more fully-featured scene-referred local contrast tool including multiple scales within one module instance and shadows/highlights control. Feedback is welcome at the pixls.us forum.
๐module controls
- base detail level
- Adjust the base detail level, which determines the scale targeted by highlights, shadows, and coarse, medium and fine details.
- higher values: affect local contrast in finer details.
- lower values: affect local contrast in coarser details.
- Press the mask display button to preview the low pass filter result used for shadows (blue) and highlights (yellow).
- The detail scales targeted by the three local contrast sliders can be previewed with their respective mask buttons (see below). Use them in conjunction with adjusting base detail level to tune the detail level you want to affect.
- highlights
- Adjust highlights at the base detail level size.
- shadows
- Adjust shadows at the base detail level size.
Note: When adjusting highlights and shadows a lower base detail level will tend to enhance local contrast in those respective regions while a higher base detail level will result in flatter local contrasts in those regions.
๐local contrast
- coarse details
- Adjust coarse, low frequency local contrasts. Click the mask display button to preview the size of the coarse details to adjust.
- medium details
- Adjust medium frequency local contrasts. Click the mask display button to preview the size of the medium details to adjust.
- fine details
- Adjust fine, high frequency local contrasts. Click the mask display button to preview the size of the fine details to adjust. Can be used for sharpening.
๐filter settings
- halo control
- Adjust the halo control of the filter.
- higher values: suppress halos at the expense of details around edges. Helps with making the effect on local contrast smoother
- lower values: allow more halos to get more local contrast and details.
- noise bias
- Helps reduce amplification of noise in the shadows by adding a bias to the luminance estimate before filtering. A higher value suppresses more shadow noise but can also reduce genuine fine detail in those areas.