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- corrections / improved comments for demosaicing and raw chromatic aberaation
- add hints about why users are shown the complete image data while using retouch & liquify
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jenshannoschwalm authored and elstoc committed Dec 8, 2023
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Showing 4 changed files with 33 additions and 27 deletions.
16 changes: 8 additions & 8 deletions content/module-reference/processing-modules/demosaic.md
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title: demosaic
id: demoasic
applicable-version: 3.8
tags:
working-color-space: Not Applicable (RAW)
tags:
working-color-space: Not Applicable (RAW)
view: darkroom
masking: false
---
@@ -12,7 +12,7 @@ Control how raw files are demosaiced.

# bayer filters

The sensor cells of a digital camera are not color-sensitive -- they are only able to record different levels of lightness. In order to obtain a color image, each cell is covered by a color filter (red, green or blue) that primarily passes light of that color. This means that each pixel of the raw image only contains information about a single color channel.
The sensor cells of a digital camera are not color-sensitive -- they are only able to record different levels of lightness. In order to obtain a color image, each cell is covered by a color filter (red, green or blue) that primarily passes light of that color. This means that each pixel of the raw image only contains information about a single color channel.

Color filters are commonly arranged in a mosaic pattern known as a Bayer filter array. A demosaic algorithm reconstructs the missing color channels by interpolation with data from the neighboring pixels. For further reading see the Wikipedia articles on [demosaicing](https://en.wikipedia.org/wiki/Demosaicing) and the [Bayer filter](http://en.wikipedia.org/wiki/Bayer_filter).

@@ -26,14 +26,14 @@ The following demosaic algorithms are available for sensors with Bayer filters:

- _AMaZE_ and _RCD_ offer better reconstruction of high-frequency content (finer details, edges, stars) but might struggle with color reconstruction overshoots or added noise in areas of low contrast. While _AMaZE_ often retains more high-frequency details it is also more prone to color overshoots than _RCD_. Since _RCD_ now offers similar performance to _PPG_, but with better results, it is now the default algorithm.

- _LMMSE_ is better suited for use on high ISO and noisy images than _AMaZE_ or _RCD_, both of which tend to generate overshooting artefacts when applied to such images. It can also be useful to manage images that exhibit Moiré patterns with other algorithms.
- _LMMSE_ is better suited for use on high ISO and noisy images than _AMaZE_ or _RCD_, both of which tend to generate overshooting artefacts when applied to such images. It can also be useful to manage images that exhibit Moiré patterns with other algorithms.

- _VNG4_ is better suited for use on images with low-frequency content (e.g. low contrast regions such as sky) but, compared to _AMaZE_ and _RCD_, it often causes loss of some high-frequency details and can sometimes add local color shifts. VNG is no longer really recommended -- for most images, other available algorithms usually provide better results.
- _VNG4_ is better suited for use on images with low-frequency content (e.g. low contrast regions such as sky) but, compared to _AMaZE_ and _RCD_, it causes loss of some high-frequency details and can sometimes add local color shifts. VNG4 is no longer recommended -- for most images, other available algorithms provide better results.

---

**Note:** The performance of the demosaic algorithms differs significantly, _AMaZE_ being by far the slowest.

---

# sensors without bayer filters
@@ -52,9 +52,9 @@ Some images have areas best demosaiced using an algorithm that preserves high fr

In dual demosaic algorithms (e.g. _RCD + VNG4_) the sensor data is demosaiced twice, first by _RCD_, _AMaZE_ or _Markesteijn 3-pass_ and then by _VNG4_. Both sets of demosaiced data are retained for subsequent processing.

The data from the high frequency algorithm is then analysed for _local data change_ and, using a threshold (there is a bit more of maths involved here), the output image is written pixel-by-pixel for each color channel using data from each demosaic algorithm weighed by the local data change.
The data from the high frequency algorithm is then analysed for _local data change_ and, using a threshold (there is a bit more of maths involved here), the output image is written pixel-by-pixel for each color channel using data from each demosaic algorithm weighed by the local data change.

In general, areas with greater detail are demosaiced by the algorithm best suited to that purpose (_RCD, AMaZe, Markesteijn 3-pass_) and any flat areas (like blue sky) are demosaiced using the second algorithm (_VNG4_).
In general, areas with greater detail are demosaiced by the algorithm best suited to that purpose (_RCD, AMaZe, Markesteijn 3-pass_) and any flat areas (like blue sky) are demosaiced using the second algorithm (_VNG4_).

_The 'local data change' is technically implemented as a gaussian-blurred single channel selection mask calculated from a combination of the threshold value and the pixels' luminance._

20 changes: 11 additions & 9 deletions content/module-reference/processing-modules/liquify.md
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title: liquify
id: liquify
applicable-version: 3.8
tags:
tags:
working-color-space: RGB
view: darkroom
masking:
masking:
---

Move pixels around by applying freestyle distortions to parts of the image using points, lines and curves.

As you might want to use data as source from the whole image you will be shown the uncropped image (possibly with the cropping rectangle as guide) while the module is active.

# nodes

Each of liquify's tools is based on nodes. A point consists of a single node and a line or curve consists of a sequence of linked nodes defining a path.

Each instance of the liquify module is limited to a maximum of 100 nodes -- for more nodes, use additional instances. However, please note that the liquify module consumes a lot of system resources.
Each instance of the liquify module is limited to a maximum of 100 nodes -- for more nodes, use additional instances. However, please note that the liquify module consumes a lot of system resources.

Drag the central point of a node to move the node around. The radius describes the area of the effect (distortion occurs only within this radius). To change the radius drag the handle at the circumference. A strength vector starting from the center describes the direction of the distortion, and its strength is depicted by the length of the vector. Change the vector by dragging its arrow head.
Drag the central point of a node to move the node around. The radius describes the area of the effect (distortion occurs only within this radius). To change the radius drag the handle at the circumference. A strength vector starting from the center describes the direction of the distortion, and its strength is depicted by the length of the vector. Change the vector by dragging its arrow head.

# points

A point consists of a single node and strength vector.
A point consists of a single node and strength vector.

Click the point icon to activate the point tool and then click on the image to place it. Hold Ctrl while clicking on the point icon to add multiple points without having to click the icon again each time. Right-click to exit creation mode.

@@ -61,7 +63,7 @@ A point can be removed by right-clicking on the center of the node.

# lines and curves

Lines and curves are sequences of points linked together by straight or curved lines. The effect is interpolated by a set of associated strength vectors.
Lines and curves are sequences of points linked together by straight or curved lines. The effect is interpolated by a set of associated strength vectors.

Click the appropriate icon to activate the line or curve tool and then click on the image to place a sequence of points forming the path. Right-click anywhere when the last point has been placed in order to finish drawing the line/curve.

@@ -73,13 +75,13 @@ lines
curves
: ![curves](./liquify/liquify_ex6.png#w50)

Ctrl+click on a line or curve segment to add a new control point. Ctrl+right-click on the center of a node to remove a control point.
Ctrl+click on a line or curve segment to add a new control point. Ctrl+right-click on the center of a node to remove a control point.

Right-click on a segment to remove the shape completely. Ctrl+Alt+click on a segment to change that segment from a line to a curve and vice versa.

# link modes

Ctrl+click on the center of a node to change the way the points of a curve are linked together. There are four modes, which correspond to different ways of handling the steepness of the bezier curve using control handles:
Ctrl+click on the center of a node to change the way the points of a curve are linked together. There are four modes, which correspond to different ways of handling the steepness of the bezier curve using control handles:

autosmooth
: This is the default mode, in which control handles are not displayed -- controls are automatically computed to give a smooth curve.
@@ -95,7 +97,7 @@ symmetrical

# view and edit nodes

Click the node tool icon to activate or deactivate the node edit tool. This displays all currently-defined distortion objects and their controls. Alternatively you can right-click on the image at any time for the same effect.
Click the node tool icon to activate or deactivate the node edit tool. This displays all currently-defined distortion objects and their controls. Alternatively you can right-click on the image at any time for the same effect.

# warps and nodes count

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title: raw chromatic aberrations
id: raw-chromatic-aberrations
applicable-version: 4.4
tags:
working-color-space: Not Applicable (RAW)
tags:
working-color-space: Not Applicable (RAW)
view: darkroom
masking: false
---

Correct chromatic aberrations of raw images.

This module currently only works for raw images recorded with a Bayer sensor (the sensor used in the majority of cameras) -- for other types of image, you should use the [_chromatic aberrations_](./chromatic-aberrations.md) module instead.
This module currently only works for raw images recorded with a Bayer sensor (the sensor used in the majority of cameras) -- for other types of image, you should use the [_chromatic aberrations_](./chromatic-aberrations.md) module instead.

The module will also not apply any corrections to any photos that have been identified as monochrome (see [developing monochrome images](../../guides-tutorials/monochrome.md) for more information).

This module expects good white balance data provided by the [_white balance_](./white-balance.md) module for best results, in most cases it's _default_ settings are sufficient.

Note that if this module is enabled, then TCA correction in the [_lens correction_](./lens-correction.md) module should be disabled, as the two modules will conflict with one another.

# module controls
@@ -22,4 +24,4 @@ iterations
: The number of iterations. For most images, "twice" is sufficient, and is the default value. Occasionally, increasing this control can give better results.

avoid colorshift
: If the module causes purple tinting, tick this box to apply a correction.
: If the module causes tinting - often pink or greenish - tick this box to apply a correction.
14 changes: 8 additions & 6 deletions content/module-reference/processing-modules/retouch.md
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title: retouch
id: retouch
applicable-version: 3.8
tags:
tags:
working-color-space: rgb
view: darkroom
masking:
masking:
---

Remove unwanted elements from your image by cloning, healing, blurring and filling using drawn shapes.

This module extends the capabilities of the deprecated [_spot removal_](./spot-removal.md) module (equivalent to this module's "clone" tool) by including a "heal" tool (based on the heal tool from GIMP), as well as "fill" and "blur" modes. It can also take advantage of [wavelet decomposition](../../darkroom/processing-modules/wavelets.md), allowing the image to be separated into layers of varying detail (from coarse to fine) which can be selectively retouched before being recombined to produce the output image.
This module extends the capabilities of the deprecated [_spot removal_](./spot-removal.md) module (equivalent to this module's "clone" tool) by including a "heal" tool (based on the heal tool from GIMP), as well as "fill" and "blur" modes. It can also take advantage of [wavelet decomposition](../../darkroom/processing-modules/wavelets.md), allowing the image to be separated into layers of varying detail (from coarse to fine) which can be selectively retouched before being recombined to produce the output image.

As you might want to use data as source from the whole image you will be shown the uncropped image (possibly with the cropping rectangle as guide) while the module is active.

# clone and heal

@@ -83,11 +85,11 @@ It can also be used with the blur tool to even out coarse blotches in the skin,
The _retouch tools_ section consists of two items:

shapes
: The number after the _shapes_ label indicates how many shapes have been placed on the image, either directly or within a wavelet layer.
: The number after the _shapes_ label indicates how many shapes have been placed on the image, either directly or within a wavelet layer.

: Click on one of the shape icons to draw a new shape on the image (see [drawn masks](../../darkroom/masking-and-blending/masks/drawn.md) for details).
: Click on one of the shape icons to draw a new shape on the image (see [drawn masks](../../darkroom/masking-and-blending/masks/drawn.md) for details).

: Ctrl+click on a shape icon to draw multiple shapes continuously (right-click to cancel).
: Ctrl+click on a shape icon to draw multiple shapes continuously (right-click to cancel).

: Click the _show and edit shapes_ ![retouch-shapes-icon](./retouch/rt-shapes-icon.png#icon) button to show and edit any existing shapes for the currently-selected wavelet scale.

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