Dynamic Range Compression - Revision history

DrSlony at 12:14, 9 March 2023

2023-03-09T12:14:18Z

← Older revision		Revision as of 12:14, 9 March 2023
Line 1:		Line 1:
	~~<div class="pagetitle">Dynamic Range Compression</div>~~

	== Introduction ==		== Introduction ==

Line 17:		Line 15:
	Use this tool when the dynamic range of the photographed scene is too high to be reproduced on your monitor in an aesthetically pleasing way, that is when you find that the difference between the dark tones and the bright tones (the contrast) is so strong that there is a lack of detail in those areas.		Use this tool when the dynamic range of the photographed scene is too high to be reproduced on your monitor in an aesthetically pleasing way, that is when you find that the difference between the dark tones and the bright tones (the contrast) is so strong that there is a lack of detail in those areas.

	~~'''Note for~~ panorama~~'s'''~~ The effects of this tool depend on the dynamic range (and histogram) of the image being edited. If you are processing a series of images intended for stitching, where each image contains a section of a scene adjacent to the one before it, even if you were to apply identical parameters to these images using this tool, the end results would not be consistent - there would be sudden changes in brightness between adjacent images. Do not use this Dynamic Range Compression tool on the source images. If you need to compress the dynamic range across a series of images in a consistent way, use a curve instead. You can, however, use this tool on the stitched panorama.		Heads-up panorama stitchers! The effects of this tool depend on the dynamic range (and histogram) of the image being edited. If you are processing a series of images intended for stitching, where each image contains a section of a scene adjacent to the one before it, even if you were to apply identical parameters to these images using this tool, the end results would not be consistent - there would be sudden changes in brightness between adjacent images. Do not use this Dynamic Range Compression tool on the source images. If you need to compress the dynamic range across a series of images in a consistent way, use a curve instead. You can, however, use this tool on the stitched panorama.

			[[File:DRC-Example.jpg\|thumb\|Demonstration of the effects of the "amount" and "detail" parameters.]]

	== Interface ==		== Interface ==

	~~The tool provides three sliders.~~		=== Amount ===
	* ''Amount'' sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram).
	* ''Detail~~'' sets~~ how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast.		Sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram).
	* ''Anchor'' biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.
			=== Detail ===

			Sets how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast.

	~~The example below shows the typical effects of each slider (click to enlarge).~~		=== Anchor ===

	~~[[File:DRC-Example~~.~~jpg]]~~		Biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.

Thanatomanic: List and italics

2021-06-17T08:48:19Z

List and italics

← Older revision		Revision as of 08:48, 17 June 2021
Line 21:		Line 21:
	== Interface ==		== Interface ==

	The tool provides three sliders. ~~The '~~''Amount''' sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram). ~~The '~~''Detail''' sets how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast. ~~The '~~''Anchor''' biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.		The tool provides three sliders.
			* ''Amount'' sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram).
			* ''Detail'' sets how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast.
			* ''Anchor'' biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.

	The example below shows the typical effects of each slider (click to enlarge).		The example below shows the typical effects of each slider (click to enlarge).

	[[File:DRC-Example.jpg]]		[[File:DRC-Example.jpg]]

Thanatomanic: /* Interface */

2021-06-17T08:46:54Z

Interface

← Older revision		Revision as of 08:46, 17 June 2021
Line 23:		Line 23:
	The tool provides three sliders. The '''Amount''' sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram). The '''Detail''' sets how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast. The '''Anchor''' biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.		The tool provides three sliders. The '''Amount''' sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram). The '''Detail''' sets how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast. The '''Anchor''' biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.

	The example below shows the typical effects of each slider.		The example below shows the typical effects of each slider (click to enlarge).

	[[File:DRC-Example.jpg]]		[[File:DRC-Example.jpg]]

Thanatomanic: Update text and include sample image

2021-06-17T08:45:18Z

Update text and include sample image

← Older revision		Revision as of 08:45, 17 June 2021
Line 21:		Line 21:
	== Interface ==		== Interface ==

	~~===~~ Amount ~~===~~		The tool provides three sliders. The '''Amount''' sets the strength of the compression. Higher values lead to a narrower dynamic range (you can easily see the effect by observing the histogram). The '''Detail''' sets how much local contrast is preserved. Positive values reduce the compression in favor of more contrast, negative values reduce the contrast. The '''Anchor''' biases the compression towards the shadows or highlights, effectively functioning as an exposure compensation.

	~~Sets~~ the ~~amount~~ of ~~compression, where higher values lead to more dynamic range compression~~.		The example below shows the typical effects of each slider.

	~~=== Detail ===~~		[[File:DRC-Example.jpg]]

	~~The amount of detail that is preserved can be tuned with this parameter. Negative values smooth the image by reducing local contrast, while positive values increase it.~~

	~~=== Anchor ===~~

	~~This parameter biases the compression towards the shadows or the highlights. It functions in effect as an exposure compensation~~.

Thanatomanic: /* Usage */

2021-06-17T08:03:43Z

Usage

← Older revision		Revision as of 08:03, 17 June 2021
Line 17:		Line 17:
	Use this tool when the dynamic range of the photographed scene is too high to be reproduced on your monitor in an aesthetically pleasing way, that is when you find that the difference between the dark tones and the bright tones (the contrast) is so strong that there is a lack of detail in those areas.		Use this tool when the dynamic range of the photographed scene is too high to be reproduced on your monitor in an aesthetically pleasing way, that is when you find that the difference between the dark tones and the bright tones (the contrast) is so strong that there is a lack of detail in those areas.

	~~Heads-up~~ panorama ~~stitchers!~~ The effects of this tool depend on the dynamic range (and histogram) of the image being edited. If you are processing a series of images intended for stitching, where each image contains a section of a scene adjacent to the one before it, even if you were to apply identical parameters to these images using this tool, the end results would not be consistent - there would be sudden changes in brightness between adjacent images. Do not use this Dynamic Range Compression tool on the source images. If you need to compress the dynamic range across a series of images in a consistent way, use a curve instead. You can, however, use this tool on the stitched panorama.		'''Note for panorama's''' The effects of this tool depend on the dynamic range (and histogram) of the image being edited. If you are processing a series of images intended for stitching, where each image contains a section of a scene adjacent to the one before it, even if you were to apply identical parameters to these images using this tool, the end results would not be consistent - there would be sudden changes in brightness between adjacent images. Do not use this Dynamic Range Compression tool on the source images. If you need to compress the dynamic range across a series of images in a consistent way, use a curve instead. You can, however, use this tool on the stitched panorama.

	== Interface ==		== Interface ==

Thanatomanic: Rewritten more compactly

2021-06-17T08:02:46Z

Rewritten more compactly

← Older revision		Revision as of 08:02, 17 June 2021
Line 3:		Line 3:
	== Introduction ==		== Introduction ==

	Dynamic range ~~in broad terms~~ is the ratio of the largest to the smallest value of a measured signal. ~~There are various things you as~~ a ~~photographer have~~ to ~~deal with which have~~ a ~~dynamic range of their own - human [https://en.wikipedia.org/wiki/Dynamic_range#Human_perception visual perception]~~ has ~~a dynamic range (you can see~~ very ~~faint stars at night~~ and ~~you can see a bright sky during daytime~~, ~~though not both at once), your monitor has~~ a dynamic range ~~(far lower than human vision)~~, as ~~does your camera~~'~~s sensor and the electronics which process the signal captured by the sensor. The Dynamic Range Compression tool is used to compress and redistribute the~~ dynamic range ~~of the~~ scene ~~captured in a photograph~~.		Dynamic range is the ratio of the largest to the smallest value of a measured signal. In photography it commonly refers to the ratio of the brightest element of a scene to the darkest. An outdoor scene on a very foggy day commonly has very little difference between the brightest and darkest elements, which is known as a ''low dynamic range'' scene. In contrast, an indoor scene with a visible sunny sky through a window is known as a ''high dynamic range'' scene.

	The dynamic range of ~~the~~ scene is the ~~ratio~~ of the ~~brightest element in~~ the scene ~~to the darkest~~. If you ~~imagine an outdoor scene on a~~ very ~~foggy day, the brightest element would not appear much brighter~~ from the ~~darkest element~~, so the ~~scene is said to have a low~~ dynamic range. ~~On the other hand~~, ~~if you were~~ to ~~stand indoors on a sunny day, the sun-lit clouds outside would appear far brighter than the lamp-lit room, let alone the dark corners of the room - this is a~~ high dynamic ~~range scene~~.		The dynamic range of a scene can easily exceed the dynamic range of the "sensor" that captures the scene. The [https://en.wikipedia.org/wiki/Dynamic_range#Human_perception human visual system] has an adaptive and wide dynamic range (you can see faint stars at night but also bright skies during day). This is very different from the fixed, lower dynamic range of your camera sensor and the (usually even lower) dynamic range of your monitor. As such, photography and image processing needs to deal with mapping high dynamic ranges to lower ones.

	~~The~~ dynamic range ~~of the scene being captured usually exceeds the dynamic range of the viewing device (monitor, laptop, smartphone). To show the scene on the viewing device, generally two things can happen~~: either a ~~certain segment~~ of the ~~dynamic range which falls~~ outside ~~of that which~~ the ~~monitor can reproduce is discarded~~ (~~the sky outside is clipped white so the you can see the inside of the room, or the sky outside is reproduced at the cost of the room being clipped black~~), or the ~~dynamic range of the scene can be compressed~~ so that ~~both~~ the ~~dark and~~ the ~~light areas are visible,~~ and ~~that~~ is ~~where this tool comes into play~~.		In general there are two ways to handle dynamic range changes: either discard a portion of the data outside the destination range (e.g. clipping highlights), or compress the data so that it fits the destination range. The Dynamic Range Compression tool uses the latter approach based on the [http://www.cs.huji.ac.il/~danix/hdr/ Gradient Domain High Dynamic Range Compression] algorithm developed by R. Fattal and coworkers. This algorithm is often simply referred to as "Fattal", e.g. in Luminance HDR.

	The ~~Dynamic Range Compression tool is used~~ to ~~compress~~ the ~~dynamic range~~ of ~~an image~~, ~~reducing highlights~~ and ~~lifting shadows. It~~ is ~~based on the paper~~ [~~http://www.cs.huji.ac.il/~danix/hdr/ Gradient Domain High Dynamic Range Compression~~], ~~referred to in~~ other ~~software~~ such as ~~Luminance HDR simply as "Fattal"~~.		The algorithm uses two parameters to control the compression (α and β) which can be tuned by the "detail" and "amount" sliders of the tool, respectively. The tool operates in RGB space and is applied right after [[Noise_Reduction\|Noise Reduction]] and [[Haze_Removal\|Haze Removal]], but before other tone curve adjustments such as the [[Exposure]] controls.

	The tool operates in RGB space and is applied right after [[Noise_Reduction\|Noise Reduction]] and [[Haze_Removal\|Haze Removal]], but before other tone curve adjustments such as the [[Exposure]] controls.		N.B. There are alternative ways of compressing the dynamic range using other tools. The simplest would be a negative contrast value in the [[Exposure]] tool to reduce (or rather to redistribute) the dynamic range, however the effect would most likely appear flat and unappealing. A curve gives more control over the process, but may need a lot of fine-tuning.

	~~The "detail" slider corresponds to the α (alpha) parameter in the paper, and the "amount" slider corresponds to β (beta)~~.

	There are alternative ways of compressing the dynamic range using other tools. The ~~most simple~~ would be a negative contrast value in the [[Exposure]] tool to reduce (or rather to redistribute) the dynamic range, however the effect would most likely appear flat and unappealing. A curve gives ~~one~~ more control over the process, ~~however this tool is designed specifically for the task~~.

	== Usage ==		== Usage ==

DrSlony at 21:41, 9 December 2019

2019-12-09T21:41:00Z

← Older revision		Revision as of 21:41, 9 December 2019
Line 1:		Line 1:
			<div class="pagetitle">Dynamic Range Compression</div>

	== Introduction ==		== Introduction ==

DrSlony at 20:16, 26 November 2018

2018-11-26T20:16:39Z

← Older revision		Revision as of 20:16, 26 November 2018
Line 11:		Line 11:
	The tool operates in RGB space and is applied right after [[Noise_Reduction\|Noise Reduction]] and [[Haze_Removal\|Haze Removal]], but before other tone curve adjustments such as the [[Exposure]] controls.		The tool operates in RGB space and is applied right after [[Noise_Reduction\|Noise Reduction]] and [[Haze_Removal\|Haze Removal]], but before other tone curve adjustments such as the [[Exposure]] controls.

	The "detail" slider corresponds to the α (alpha) parameter in the paper, and the "amount" slider corresponds to β (beta).		The "detail" slider corresponds to the α (alpha) parameter in the paper, and the "amount" slider corresponds to β (beta).

	There are alternative ways of compressing the dynamic range using other tools. The most simple would be a negative contrast value in the [[Exposure]] tool to reduce (or rather to redistribute) the dynamic range, however the effect would most likely appear flat and unappealing. A curve gives one more control over the process, however this tool is designed specifically for the task.		There are alternative ways of compressing the dynamic range using other tools. The most simple would be a negative contrast value in the [[Exposure]] tool to reduce (or rather to redistribute) the dynamic range, however the effect would most likely appear flat and unappealing. A curve gives one more control over the process, however this tool is designed specifically for the task.
Line 25:		Line 25:
	=== Amount ===		=== Amount ===

	Sets the amount of compression, where ~~lower~~ values ~~mean less~~ compression~~. The default value of 20 gives a reasonable starting point~~.		Sets the amount of compression, where higher values lead to more dynamic range compression.

	=== Detail ===		=== Detail ===

	The amount of detail that is preserved can be tuned with this parameter. Negative values smooth the image, positive values recover detail that is lost during the tonemapping. Technically, this parameter attenuates which contrast-rich areas get compressed or not, and is linked to the value α from the original research paper. The default value of 0 gives no detail recovery, and usually a slightly positive value is desired.		The amount of detail that is preserved can be tuned with this parameter. Negative values smooth the image by reducing local contrast, while positive values increase it.

	=== Anchor ===		=== Anchor ===

	~~The~~ compression ~~can be biased~~ towards shadows or highlights ~~by setting this parameter. Lower values give overall darker images, and higher values give overall lighter images~~. ~~The default value is 50, resulting~~ in ~~no bias. Technically, this parameter is linked to the value β from the original research paper~~.		This parameter biases the compression towards the shadows or the highlights. It functions in effect as an exposure compensation.

DrSlony at 19:41, 26 November 2018

2018-11-26T19:41:27Z

← Older revision		Revision as of 19:41, 26 November 2018
Line 1:		Line 1:
	== Introduction ==		== Introduction ==

	Dynamic range in broad terms is the ratio of the largest to the smallest value of a measured signal. There are various things you as a photographer have to deal with which have a dynamic range of their own - human [https://en.wikipedia.org/wiki/Dynamic_range#Human_perception visual perception] has a dynamic range (you can see very faint stars at night and you can see a bright sky during daytime, though not both at once), your monitor has a dynamic range (far lower than human vision), as does your camera's sensor and the electronics which process the signal captured by the sensor. ~~This~~ tool is used to ~~work with~~ the dynamic range of the scene ~~you're capturing~~.		Dynamic range in broad terms is the ratio of the largest to the smallest value of a measured signal. There are various things you as a photographer have to deal with which have a dynamic range of their own - human [https://en.wikipedia.org/wiki/Dynamic_range#Human_perception visual perception] has a dynamic range (you can see very faint stars at night and you can see a bright sky during daytime, though not both at once), your monitor has a dynamic range (far lower than human vision), as does your camera's sensor and the electronics which process the signal captured by the sensor. The Dynamic Range Compression tool is used to compress and redistribute the dynamic range of the scene captured in a photograph.

	The dynamic range of the scene is the ratio of the brightest element in the scene to the darkest. If you imagine an outdoor scene on a very foggy day, the brightest element would not appear much brighter from the darkest element, so the scene is said to have a low dynamic range. On the other hand, if you were to stand indoors on a sunny day, the sun-lit clouds outside would appear far brighter than the lamp-lit room, let alone the dark corners of the room - this is a high dynamic range scene.		The dynamic range of the scene is the ratio of the brightest element in the scene to the darkest. If you imagine an outdoor scene on a very foggy day, the brightest element would not appear much brighter from the darkest element, so the scene is said to have a low dynamic range. On the other hand, if you were to stand indoors on a sunny day, the sun-lit clouds outside would appear far brighter than the lamp-lit room, let alone the dark corners of the room - this is a high dynamic range scene.

DrSlony at 19:40, 26 November 2018

2018-11-26T19:40:16Z

← Older revision		Revision as of 19:40, 26 November 2018
Line 1:		Line 1:
	== Introduction ==		== Introduction ==

	Dynamic range in broad terms is the ratio of the largest to the smallest ~~values~~ of a measured signal. There are various things you as a photographer have to deal with which ~~all~~ have a dynamic range of their own - human [https://en.wikipedia.org/wiki/Dynamic_range#Human_perception visual perception] has a dynamic range (you can see very faint stars at night and you can see a bright sky during daytime, though not both at once), your monitor has a dynamic range (far lower than human vision), as does your camera's sensor and the electronics which process the captured ~~signals~~. This tool is used to work with the dynamic range of the scene you're capturing.		Dynamic range in broad terms is the ratio of the largest to the smallest value of a measured signal. There are various things you as a photographer have to deal with which have a dynamic range of their own - human [https://en.wikipedia.org/wiki/Dynamic_range#Human_perception visual perception] has a dynamic range (you can see very faint stars at night and you can see a bright sky during daytime, though not both at once), your monitor has a dynamic range (far lower than human vision), as does your camera's sensor and the electronics which process the signal captured by the sensor. This tool is used to work with the dynamic range of the scene you're capturing.

	The dynamic range of the scene is the ratio of the brightest element in the scene to the darkest. If you imagine an outdoor scene on a very foggy day, the brightest element would not appear much brighter from the darkest element, so the scene is said to have a low dynamic range. On the other hand, if you were to stand indoors on a sunny day, the sun-lit clouds outside would appear far brighter than the lamp-lit room, let alone the dark corners of the room - this is a high dynamic range scene.		The dynamic range of the scene is the ratio of the brightest element in the scene to the darkest. If you imagine an outdoor scene on a very foggy day, the brightest element would not appear much brighter from the darkest element, so the scene is said to have a low dynamic range. On the other hand, if you were to stand indoors on a sunny day, the sun-lit clouds outside would appear far brighter than the lamp-lit room, let alone the dark corners of the room - this is a high dynamic range scene.