Color Pipeline - Revision history

Patapom at 16:07, 20 November 2016

2016-11-20T16:07:09Z

Patapom at 16:05, 20 November 2016

2016-11-20T16:05:08Z

Patapom at 16:52, 12 January 2012

2012-01-12T16:52:31Z

Patapom at 16:24, 1 January 2012

2012-01-01T16:24:46Z

Patapom at 16:22, 1 January 2012

2012-01-01T16:22:36Z

Patapom at 19:53, 30 December 2011

2011-12-30T19:53:43Z

Patapom at 15:43, 30 December 2011

2011-12-30T15:43:42Z

Patapom at 14:29, 30 December 2011

2011-12-30T14:29:38Z

Patapom at 14:15, 30 December 2011

2011-12-30T14:15:53Z

Patapom at 22:44, 29 December 2011

2011-12-29T22:44:00Z

@@ Line 5: / Line 5: @@
 * The first level is the article itself, which is going to attempt to sum up in a very general way of what I could grasp of the vast subject that is color perception
 * It will sometimes refer to other pages called [[Colorimetry]] and [[Color Profile]] where technical information regarding specific details are available
-* The [[Colorimetry]] and [[Color Profile]] pages will sometimes themselves refer to even more detailed information and equations (''e.g.'' [[Color_Transforms]], [[Colorimetry_Illuminant_Computation]], [[Image_Metadata]])
+* The [[Colorimetry]] and [[Color Profile]] pages will sometimes themselves refer to even more detailed information and equations (''e.g.'' [[Color_Transforms]], [[Illuminant_Computation]], [[Image_Metadata]])

@@ Line 5: / Line 5: @@
 * The first level is the article itself, which is going to attempt to sum up in a very general way of what I could grasp of the vast subject that is color perception
 * It will sometimes refer to other pages called [[Colorimetry]] and [[Color Profile]] where technical information regarding specific details are available
-* The [[Colorimetry]] and [[Color Profile]] pages will sometimes themselves refer to even more detailed information and equations (''e.g.'' [[Color_Transforms]], [[Colorimetry_DIlluminant_Computation]], [[Image_Metadata]])
+* The [[Colorimetry]] and [[Color Profile]] pages will sometimes themselves refer to even more detailed information and equations (''e.g.'' [[Color_Transforms]], [[Colorimetry_Illuminant_Computation]], [[Image_Metadata]])

← Older revision		Revision as of 16:52, 12 January 2012
Line 1:		Line 1:
−	=The Color Pipeline : A Compendium of colorimetry and light perception for the Computer Graphics programmer=	+	=The Color Pipeline : A Compendium about colorimetry and light perception for the Computer Graphics programmer=
	This article is a poor (and still confusing) attempt at gathering all the important notions and is a digest of the enormous amount (!!) of available informations about colors, color spaces, color profiles, color corrections, color management, color grabbing and color display.		This article is a poor (and still confusing) attempt at gathering all the important notions and is a digest of the enormous amount (!!) of available informations about colors, color spaces, color profiles, color corrections, color management, color grabbing and color display.

@@ Line 1: / Line 1: @@
 =The Color Pipeline : A Compendium of colorimetry and light perception for the Computer Graphics programmer=
 This article has 3 levels of knowledge :
-* The first level is the article itself, which is going to attempt to sum up in a very general what I could grasp of the vast subject (!!) that is color perception
+* The first level is the article itself, which is going to attempt to sum up in a very general way of what I could grasp of the vast subject that is color perception
-* The article will sometimes refer to other pages called [[Colorimetry]] and [[Color Profile]] where technical informations regarding specific details are available
+* It will sometimes refer to other pages called [[Colorimetry]] and [[Color Profile]] where technical information regarding specific details are available
-* The [[Colorimetry]] page itself will sometimes refer to even more detailed informations and equations (''e.g.'' [[Color_Transforms]], [[Colorimetry_DIlluminant_Computation]], [[Image_Metadata]])
+* The [[Colorimetry]] and [[Color Profile]] pages will sometimes themselves refer to even more detailed information and equations (''e.g.'' [[Color_Transforms]], [[Colorimetry_DIlluminant_Computation]], [[Image_Metadata]])

@@ Line 4: / Line 4: @@
 * The first level is the article itself, which is going to attempt to sum up in a very general what I could grasp of the vast subject (!!) that is color perception
 * The article will sometimes refer to other pages called [[Colorimetry]] and [[Color Profile]] where technical informations regarding specific details are available
-* The [[Colorimetry]] page itself will sometimes refer to even more detailed informations and equations
+* The [[Colorimetry]] page itself will sometimes refer to even more detailed informations and equations (''e.g.'' [[Color_Transforms]], [[Colorimetry_DIlluminant_Computation]], [[Image_Metadata]])
 This article is a poor attempt at gathering all the important notions and is a digest of the enormous amount of available informations about colors, color spaces, color profiles, color corrections, color management, color grabbing and color display.
@@ Line 60: / Line 60: @@
 * Apply gamma-compression or not
 * Use an explicit Color Profile or not
-* Store metadata or not
+* Store [[Image_Metadata|metadata]] or not
 * Use the RGB color space or some other color spaces like YCbCr or CIELAB in the case of TIFF extensions (even CMYK for printing purpose but we will ignore that since it's not part of our pipeline)
-Basically, the RGB Color Space is used in almost every case. As stated in the previous [[Color_Pipeline#Acquisition||Acquisition]] section, RGB is the method of choice due to hardware constraints but also a device-dependent format. This is why the most recent profiles usually include '''metadata''' that give informations about the Color Profile the image was created with.
+Basically, the RGB Color Space is used in almost every case. As stated in the previous [[Color_Pipeline#Acquisition||Acquisition]] section, RGB is the method of choice due to hardware constraints but also a device-dependent format. This is why the most recent profiles usually include [[Image_Metadata|'''metadata''']] that give informations about the Color Profile the image was created with.
 If each stage of the pipeline follows the Color Profile correctly from beginning to end, then ultimately we will display the same colors independently of the display device used, and these colors will be the same no matter how many storage and processing stages the image sustained, no matter the camera or software used to create them.
@@ Line 122: / Line 122: @@
 Raw image files are sometimes called digital negatives, as they fulfill the same role as negatives in film photography: that is, the negative is not directly usable as an image, but has all of the information needed to create an image. Likewise, the process of converting a raw image file into a viewable format is sometimes called developing a raw image, by analogy with the film development process used to convert photographic film into viewable prints. The selection of the final choice of image rendering is part of the process of white balancing and color grading.
-Like a photographic negative, a raw digital image may have a wider dynamic range or color gamut than the eventual final image format, and it preserves most of the information of the captured image. The purpose of raw image formats is to save, with minimum loss of information, data obtained from the sensor, and the conditions surrounding the capturing of the image (the metadata).
+Like a photographic negative, a raw digital image may have a wider dynamic range or color gamut than the eventual final image format, and it preserves most of the information of the captured image. The purpose of raw image formats is to save, with minimum loss of information, data obtained from the sensor, and the conditions surrounding the capturing of the image (the [[Image_Metadata|metadata]]).
 Although RAW is a good choice for exporting images, it cannot be read back by a 3D renderer directly as the image will certainly require a lot of processing prior to be saved to a "ready format" that we will later be able to use directly.

← Older revision		Revision as of 19:53, 30 December 2011
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	==Acquisition==		==Acquisition==
−	[[File:Eye_cones_RGB_response.jpg\|thumb\|300px\|RGB response curve of the eye's cones.Source: http://www.jands.com.au/support/product_support/lighting_technical_materials/what_to_look_for_when_judging_an_led_fixture146s_colour_mixing_capabilities133]]
−	[[File:Luxeon_vs_cones_RGB_LED.png\|thumb\|300px\|RGB spectrum of RGB leds compared to eye response (The spectra for these LEDs were pulled from the Philips “Luxeon Rebel” datasheet).Source: http://www.jands.com.au/support/product_support/lighting_technical_materials/what_to_look_for_when_judging_an_led_fixture146s_colour_mixing_capabilities133)]]
	First, color acquisition by a camera sensor or a scanner is not device-independent at all.		First, color acquisition by a camera sensor or a scanner is not device-independent at all.

@@ Line 1: / Line 1: @@
 =The Color Pipeline : A Compendium of colorimetry and light perception for the Computer Graphics programmer=
-This article has 3 knowledge levels :
+This article has 3 levels of knowledge :
 * The first level is the article itself, which is going to attempt to sum up in a very general what I could grasp of the vast subject (!!) that is color perception
-* The article will sometimes refer to another page called [[Colorimetry]] where technical informations regarding specific details are available
+* The article will sometimes refer to other pages called [[Colorimetry]] and [[Color Profile]] where technical informations regarding specific details are available
 * The [[Colorimetry]] page itself will sometimes refer to even more detailed informations and equations
-This article is a poor attempt at gathering all the important notions and is a digest of the enormous amount of available informations about colors, color spaces, color profiles, color corrections, color grabbing and color display.
+This article is a poor attempt at gathering all the important notions and is a digest of the enormous amount of available informations about colors, color spaces, color profiles, color corrections, color management, color grabbing and color display.
 =Quick overview of the pipeline=
-The typical color pipeline for a photographer would imply the acquisition by a camera, storage to the disk (usually in JPEG or RAW), processing (in Photoshop or Gimp) then perhaps another storage and finally a hard print to paper.
+The typical color pipeline for a photographer would imply the acquisition by a camera, storage to the disk (usually in JPEG or RAW), processing (in Adobe Photoshop, Adobe Lightroom or Gimp) then perhaps another storage stage and finally a hard print to paper.
 In CG, the pipeline is quite larger and no longer limited to a single unique pipeline since images can come from different sources (a camera, a hand-painted texture, a rendering software).
@@ Line 16: / Line 16: @@
 Typically, you have the following scenarii for image generation:
 :Real Scene &rarr; Camera &rarr; Storage (real scene acquisition scenario)
-:Photoshop &rarr; Storage (hand-painted scenario)
+:Photoshop &rarr; Storage (hand-painting scenario)
 :Renderer &rarr; Storage (generated scenario)
@@ Line 30: / Line 30: @@
 It would be easy if:
 * The camera could have the same adaptation range as the eye and store the luminance in a lossless, device-independent HDR format.
-* All the various stages in the pipelines would work in device-independent linear-space colors.
+* Every stage in the pipelines would work in device-independent linear-space colors.
 * The display device could render the same luminance levels as the ones stored by the camera.
-Unfortunately, there are various clipping, compression and transform limitations in each stage that we will attempt to quickly describe in an overview of the pipeline.
+Unfortunately, there are various clipping, compression and transform limitations at each stage that we will attempt to describe in a quick overview of the pipeline.
@@ Line 43: / Line 43: @@
 Although, as we will see later, [http://en.wikipedia.org/wiki/Charge-coupled_device CCD (charge-coupled device) sensors] capture a value proportional to the light intensity reaching the sensor, the sensor has 1) a limited range (bit depth) and 2) the RGB color filter has its very own response curve that is camera-specific.
-In short, each camera has its own '''Color Profile'''. Even 2 cameras of the same model and brand can have 2 different Color Profiles, and a camera will see its Color Profile change due to aging of the sensor.
+In short, each camera has its own '''Color Profile'''. Even 2 cameras of the same model and brand can have 2 different Color Profiles. Also, a camera will see its Color Profile change due to sensor degradation/aging.
 The '''Color Profile''' of an image is the most important concept we need to deal with as it intervenes in every stage of the pipeline. It's inherent to all stages of the pipeline because (almost) all of these stages work with '''RGB Color Space''' which is maybe the most well known and relevant color space because imposed by hardware but, as we saw, the sensors/emitters all have their own '''profile''', making them (and the RGB Color Space) inherently '''device-dependent'''.
-In conclusion: RGB is the easiest and most commonly used color space but also the least reliable in terms of transfer from one device to the other. This is why we need '''Color Management''' and '''Color Profiles''' to ensure the colors stay "the same" throughout the entire pipeline.
+In conclusion: RGB maybe the easiest and most commonly used color space but also is the least reliable in terms of transfer from one device to the other. This is why we need '''Color Management''' and '''Color Profiles''' to ensure the colors stay "the same" throughout the entire pipeline.
 ==Storage==
-Image storage, on top of storing images in different Color Profiles, is a difficult task due to the multitude of existing image formats and their limitations.
+Image storage, on top of storing images in different Color Profiles, is a difficult task due to the multitude of image formats and their limitations : there is no one-size-fits-all perfect format.
-A few of the commonly used image formats we will be dealing with include JPEG, TIFF, PNG, RAW, BMP, GIF, TGA, DDS and HDR.
+A few of the commonly used image formats we will be dealing with include JPEG, PNG, TIFF, BMP, GIF, TGA, RAW, DDS and HDR.
 Each format can:
@@ Line 66: / Line 66: @@
-Basically, the RGB Color Space is used in almost every case. As stated in the previous [[Color_Pipeline#Acquisition Acquisition]] section, RGB is the method of choice due to hardware constraints but also a device-dependent format. This is why the most recent profiles usually include '''metadata''' that give informations about the Color Profile the image was created with.
+Basically, the RGB Color Space is used in almost every case. As stated in the previous [[Color_Pipeline#Acquisition||Acquisition]] section, RGB is the method of choice due to hardware constraints but also a device-dependent format. This is why the most recent profiles usually include '''metadata''' that give informations about the Color Profile the image was created with.
 If each stage of the pipeline follows the Color Profile correctly from beginning to end, then ultimately we will display the same colors independently of the display device used, and these colors will be the same no matter how many storage and processing stages the image sustained, no matter the camera or software used to create them.
@@ Line 72: / Line 72: @@
 ==Processing==
-We will be talking mostly about Adobe Photoshop here. Photoshop has been embedding '''Color Profiles''' and '''Color Management''' from the CS2 version, certainly due to the explosion of the digital cameras and LCD display devices market : the birth of the digital generation.
+We will be talking only about Adobe Photoshop here as it is certainly the main tool used by artists in the CG and video games industry. Photoshop has been embedding '''Color Profiles''' and '''Color Management''' from the CS2 version, certainly due to the explosion of the digital cameras and LCD display devices market : the birth of the digital generation.

@@ Line 37: / Line 37: @@
 ==Acquisition==
 First, color acquisition by a camera sensor or a scanner is not device-independent at all.
@@ Line 43: / Line 45: @@
 In short, each camera has its own '''Color Profile'''. Even 2 cameras of the same model and brand can have 2 different Color Profiles, and a camera will see its Color Profile change due to aging of the sensor.
-The '''Color Profile''' of an image is the most important concept we need to deal with as it intervenes in every stage of the pipeline. It's inherent to all stages of the pipeline because (almost) all of these stages work with '''RGB Color Space''' which is maybe the most well known and relevant color space due to the fact that cameras and display devices have RGB sensors/emitters but, as we saw, these sensors/emitter all have their own '''profile''', making them (and the RGB Color Space) inherently '''device-dependent'''.
+The '''Color Profile''' of an image is the most important concept we need to deal with as it intervenes in every stage of the pipeline. It's inherent to all stages of the pipeline because (almost) all of these stages work with '''RGB Color Space''' which is maybe the most well known and relevant color space because imposed by hardware but, as we saw, the sensors/emitters all have their own '''profile''', making them (and the RGB Color Space) inherently '''device-dependent'''.
-In conclusion: RGB is the easiest and most commonly used color space but also the least reliable in terms of transfer from one device to the other. This is why we need '''Color Management''' and '''Color Profiles'''.
+In conclusion: RGB is the easiest and most commonly used color space but also the least reliable in terms of transfer from one device to the other. This is why we need '''Color Management''' and '''Color Profiles''' to ensure the colors stay "the same" throughout the entire pipeline.

@@ Line 7: / Line 7: @@
 This article is a poor attempt at gathering all the important notions and is a digest of the enormous amount of available informations about colors, color spaces, color profiles, color corrections, color grabbing and color display.
@@ Line 39: / Line 33: @@
 * The display device could render the same luminance levels as the ones stored by the camera.
-Unfortunately, there are various clipping, compression and transform limitations in each of the described stages.
+Unfortunately, there are various clipping, compression and transform limitations in each stage that we will attempt to quickly describe in an overview of the pipeline.
 ==Acquisition==
 [[File:Bayer_pattern_on_sensor.png|thumb|300px|A [http://en.wikipedia.org/wiki/Bayer_filter Bayer filter] on a CCD]]
-The color acquisition by a camera is performed by [http://en.wikipedia.org/wiki/Charge-coupled_device CCD (charge-coupled device) sensors].
+The color acquisition by a camera is performed by [http://en.wikipedia.org/wiki/Charge-coupled_device CCD sensors].
 These sensors commonly respond to 70 percent of the incident light making them far more efficient than photographic film, which captures only about 2 percent of the incident light.
@@ Line 84: / Line 136: @@
 Finally, JPEG stores a gamma-compressed version of the image (as will be seen later) that further increases the loss of information.
 ==Taking a Picture==
 ==Artist Painting==

@@ Line 2: / Line 2: @@
 This article has 3 knowledge levels :
-* The first level is the article itself, which is going to attempt to sum up what I could grasp of the vast subject (!!) that is color perception
+* The first level is the article itself, which is going to attempt to sum up in a very general what I could grasp of the vast subject (!!) that is color perception
 * The article will sometimes refer to another page called [[Colorimetry]] where technical informations regarding specific details are available
-* The [[Colorimetry]] page itself will sometimes refer to even more detailed informations and equations that will help performing various tasks
+* The [[Colorimetry]] page itself will sometimes refer to even more detailed informations and equations
 This article is a poor attempt at gathering all the important notions and is a digest of the enormous amount of available informations about colors, color spaces, color profiles, color corrections, color grabbing and color display.
@@ Line 10: / Line 10: @@
 =Color Spaces=
 ==RGB==
 ==XYZ==
@@ Line 34: / Line 35: @@
 It would be easy if:
-* The camera could have the same adaptation range as the eye and store the luminance in a lossless HDR format.
+* The camera could have the same adaptation range as the eye and store the luminance in a lossless, device-independent HDR format.
-* All the various stages in the pipelines would work in linear-space colors.
+* All the various stages in the pipelines would work in device-independent linear-space colors.
 * The display device could render the same luminance levels as the ones stored by the camera.
@@ Line 58: / Line 59: @@
 This means the RGB values stored by the camera internally is proportional to the perceived light intensity in the Red, Green and Blue parts of the spectrum. But that does not mean these values are standardized and are the same for all cameras !
-Ignoring the minor discrepancies of optics, the main problem comes from the RGB filters applied to the CCD that will react differently depending on the coating material and method used by the camera manufacturer. Each camera has its own [[http://wiki.patapom.com/index.php/Color_Pipeline#Color_Profiles|Color Profile]] which we will discuss later. But this is where the nightmare begins ! Check a nice video showing you how to correctly setup the color profile of your camera: http://www.pinkbike.com/news/Camera-color-Profile-2010.html.
+Ignoring the minor discrepancies of optics, the main problem comes from the RGB filters applied to the CCD that will react differently depending on the coating material and method used by the camera manufacturer. Each camera has its own [[Color_Pipeline#Color_Profiles|Color Profile]] which we will discuss later. But this is where the nightmare begins ! Check a nice video showing you how to correctly setup the color profile of your camera: http://www.pinkbike.com/news/Camera-color-Profile-2010.html.
@@ Line 72: / Line 73: @@
 Although RAW is a good choice for exporting images, it cannot be read back by a 3D renderer directly as the image will certainly require a lot of processing prior to be saved to a "ready format" that we will later be able to use directly.
-Typical processing in the CG pipeline involves white balancing, color grading, level and curve adjustment as well as a fair deal of hand painting (e.g. tiling) by artists that will transform the raw image into a usable texture. This is described later in the [[http://wiki.patapom.com/index.php/Color_Pipeline#Processing Processing]] section.
+Typical processing in the CG pipeline involves white balancing, color grading, level and curve adjustment as well as a fair deal of hand painting (e.g. tiling) by artists that will transform the raw image into a usable texture. This is described later in the [[Color_Pipeline#Processing|Processing]] section.
-It is important to note that RAW still stores RGB colors in the color profile of the camera as RGB is not a device-independent format.
+It is important to note that RAW still stores RGB colors in the color profile of the camera and is '''not''' a device-independent format.
 ===JPEG===
 JPEG is a very compact format that might be useful to store many images in the minimum amount of space but, although the processing software embedded in cameras is pretty good (since it was calibrated for the camera itself), it has the main disadvantage of forcing the photographer to decide immediately of the white balance and color balance to apply to the image without the possibility to retrieve the image as it was originally shot.
-Also, JPEG only supports 8 bits per component, losing quite an important deal of precision compared to the 12-bit depth of the standard CCD sensor.
+Also, JPEG is a lossy format that only supports 8 bits per component, losing quite an important deal of precision compared to the 12-bit depth of the standard CCD sensor and the lossless RAW format.
 ==Storage==