Shadows/Highlights: Difference between revisions

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Use this tool to raise the shadows or darken the highlights of an image.
<div class="pagetitle">Shadows / Highlights</div>


== Sharp Mask ==
== Introduction ==
<gallery caption="Shadows/Highlights 'Sharp mask' effect" style="clear: both" perrow=3 mode="packed">
File:Sh_sm_1.jpg|The source image.
File:Sh_sm_2.jpg|"Sharp mask" turned off.
File:Sh_sm_3.jpg|"Sharp mask" turned on.
</gallery>


In order to separate the dark areas from the light ones, a lightness mask (invisible to the user) is created. There are two algorithms for doing this; one blurs the image, while the other retains sharp edges between light and dark zones. Neither one is "better", both have their own merits. The soft mask approach can lead to halos, but it is quick. The sharp mask is slow, but it doesn't cause halos, though it can cause edge artifacts at close inspection.
Use this tool to brighten the shadows or darken the highlights of an image.
 
This tool has received a new engine in RawTherapee 5.5, it now uses an edge-aware [https://arxiv.org/abs/1505.00996 fast guided filter] to prevent halos and operates by default in RGB space to preserve saturation.
 
== Usage ==
 
Use it in moderation to preserve a natural look. If the photographed scene has a high dynamic range (very deep shadows and very bright highlights) then use the [[Dynamic Range Compression]] tool to compress the dynamic range to a more manageable level, and then optionally use this Shadows/Highlights tool on top of that.
 
== Interface ==
 
=== Color Space ===
 
Adjusting shadows and highlights in the RGB space preserves image saturation which usually looks more natural than working in L*a*b* space which tends to desaturate affected areas. However, in some cases working in RGB space may oversaturate the shadows, in which case you should switch to L*a*b* space.
 
=== Shadows ===


== Shadows ==
Allows you to brighten the darkest parts of the image
Allows you to brighten the darkest parts of the image


== Highlights ==
=== Highlights ===
 
Allows you to darken the brightest parts of the image.
Allows you to darken the brightest parts of the image.


== Tonal Width ==
=== Tonal Width ===
 
Shadows/Highlights Tonal Width allows you to control how bright an area must be for it to be affected by the highlights slider, and how dark an area must be for it to be affected by the shadows slider. Though the underlying math is a bit more complicated, think of a histogram - the highlights tonal width specifies the range of tones from the white end of the histogram which the highlights slider will affect, and the shadows tonal width specifies the range of tones from the black end of the histogram which the shadows slider will affect. The higher the tonal width value, the more tones are affected.
Shadows/Highlights Tonal Width allows you to control how bright an area must be for it to be affected by the highlights slider, and how dark an area must be for it to be affected by the shadows slider. Though the underlying math is a bit more complicated, think of a histogram - the highlights tonal width specifies the range of tones from the white end of the histogram which the highlights slider will affect, and the shadows tonal width specifies the range of tones from the black end of the histogram which the shadows slider will affect. The higher the tonal width value, the more tones are affected.


== Radius ==
=== Radius ===
 
The value of the Radius slider influences the effective area of the Shadows and Highlights sliders.
The value of the Radius slider influences the effective area of the Shadows and Highlights sliders.

Latest revision as of 21:40, 9 December 2019

Shadows / Highlights

Introduction

Use this tool to brighten the shadows or darken the highlights of an image.

This tool has received a new engine in RawTherapee 5.5, it now uses an edge-aware fast guided filter to prevent halos and operates by default in RGB space to preserve saturation.

Usage

Use it in moderation to preserve a natural look. If the photographed scene has a high dynamic range (very deep shadows and very bright highlights) then use the Dynamic Range Compression tool to compress the dynamic range to a more manageable level, and then optionally use this Shadows/Highlights tool on top of that.

Interface

Color Space

Adjusting shadows and highlights in the RGB space preserves image saturation which usually looks more natural than working in L*a*b* space which tends to desaturate affected areas. However, in some cases working in RGB space may oversaturate the shadows, in which case you should switch to L*a*b* space.

Shadows

Allows you to brighten the darkest parts of the image

Highlights

Allows you to darken the brightest parts of the image.

Tonal Width

Shadows/Highlights Tonal Width allows you to control how bright an area must be for it to be affected by the highlights slider, and how dark an area must be for it to be affected by the shadows slider. Though the underlying math is a bit more complicated, think of a histogram - the highlights tonal width specifies the range of tones from the white end of the histogram which the highlights slider will affect, and the shadows tonal width specifies the range of tones from the black end of the histogram which the shadows slider will affect. The higher the tonal width value, the more tones are affected.

Radius

The value of the Radius slider influences the effective area of the Shadows and Highlights sliders.