COLOR

  • FXGuide – ACES 2.0 with ILM’s Alex Fry

    https://draftdocs.acescentral.com/background/whats-new/

    ACES 2.0 is the second major release of the components that make up the ACES system. The most significant change is a new suite of rendering transforms whose design was informed by collected feedback and requests from users of ACES 1. The changes aim to improve the appearance of perceived artifacts and to complete previously unfinished components of the system, resulting in a more complete, robust, and consistent product.

    Highlights of the key changes in ACES 2.0 are as follows:

    • New output transforms, including:
      • A less aggressive tone scale
      • More intuitive controls to create custom outputs to non-standard displays
      • Robust gamut mapping to improve perceptual uniformity
      • Improved performance of the inverse transforms
    • Enhanced AMF specification
    • An updated specification for ACES Transform IDs
    • OpenEXR compression recommendations
    • Enhanced tools for generating Input Transforms and recommended procedures for characterizing prosumer cameras
    • Look Transform Library
    • Expanded documentation

    Rendering Transform

    The most substantial change in ACES 2.0 is a complete redesign of the rendering transform.

    ACES 2.0 was built as a unified system, rather than through piecemeal additions. Different deliverable outputs “match” better and making outputs to display setups other than the provided presets is intended to be user-driven. The rendering transforms are less likely to produce undesirable artifacts “out of the box”, which means less time can be spent fixing problematic images and more time making pictures look the way you want.

    Key design goals

    • Improve consistency of tone scale and provide an easy to use parameter to allow for outputs between preset dynamic ranges
    • Minimize hue skews across exposure range in a region of same hue
    • Unify for structural consistency across transform type
    • Easy to use parameters to create outputs other than the presets
    • Robust gamut mapping to improve harsh clipping artifacts
    • Fill extents of output code value cube (where appropriate and expected)
    • Invertible – not necessarily reversible, but Output > ACES > Output round-trip should be possible
    • Accomplish all of the above while maintaining an acceptable “out-of-the box” rendering

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    Read more: FXGuide – ACES 2.0 with ILM’s Alex Fry
  • What is a Gamut or Color Space and why do I need to know about CIE

    http://www.xdcam-user.com/2014/05/what-is-a-gamut-or-color-space-and-why-do-i-need-to-know-about-it/

     

    In video terms gamut is normally related to as the full range of colours and brightness that can be either captured or displayed.

     

    Generally speaking all color gamuts recommendations are trying to define a reasonable level of color representation based on available technology and hardware. REC-601 represents the old TVs. REC-709 is currently the most distributed solution. P3 is mainly available in movie theaters and is now being adopted in some of the best new 4K HDR TVs. Rec2020 (a wider space than P3 that improves on visibke color representation) and ACES (the full coverage of visible color) are other common standards which see major hardware development these days.

     

     

    To compare and visualize different solution (across video and printing solutions), most developers use the CIE color model chart as a reference.
    The CIE color model is a color space model created by the International Commission on Illumination known as the Commission Internationale de l’Elcairage (CIE) in 1931. It is also known as the CIE XYZ color space or the CIE 1931 XYZ color space.
    This chart represents the first defined quantitative link between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. Or basically, the range of color a typical human eye can perceive through visible light.

     

    Note that while the human perception is quite wide, and generally speaking biased towards greens (we are apes after all), the amount of colors available through nature, generated through light reflection, tend to be a much smaller section. This is defined by the Pointer’s Chart.

     

    In short. Color gamut is a representation of color coverage, used to describe data stored in images against available hardware and viewer technologies.

     

    Camera color encoding from
    https://www.slideshare.net/hpduiker/acescg-a-common-color-encoding-for-visual-effects-applications

     

    CIE 1976

    http://bernardsmith.eu/computatrum/scan_and_restore_archive_and_print/scanning/

     

    https://store.yujiintl.com/blogs/high-cri-led/understanding-cie1931-and-cie-1976

     

    The CIE 1931 standard has been replaced by a CIE 1976 standard. Below we can see the significance of this.

     

    People have observed that the biggest issue with CIE 1931 is the lack of uniformity with chromaticity, the three dimension color space in rectangular coordinates is not visually uniformed.

     

    The CIE 1976 (also called CIELUV) was created by the CIE in 1976. It was put forward in an attempt to provide a more uniform color spacing than CIE 1931 for colors at approximately the same luminance

     

    The CIE 1976 standard colour space is more linear and variations in perceived colour between different people has also been reduced. The disproportionately large green-turquoise area in CIE 1931, which cannot be generated with existing computer screens, has been reduced.

     

    If we move from CIE 1931 to the CIE 1976 standard colour space we can see that the improvements made in the gamut for the “new” iPad screen (as compared to the “old” iPad 2) are more evident in the CIE 1976 colour space than in the CIE 1931 colour space, particularly in the blues from aqua to deep blue.

     

     

    https://dot-color.com/2012/08/14/color-space-confusion/

    Despite its age, CIE 1931, named for the year of its adoption, remains a well-worn and familiar shorthand throughout the display industry. CIE 1931 is the primary language of customers. When a customer says that their current display “can do 72% of NTSC,” they implicitly mean 72% of NTSC 1953 color gamut as mapped against CIE 1931.

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    Read more: What is a Gamut or Color Space and why do I need to know about CIE
  • OpenColorIO standard

    http://opencolorio.org/

     

    https://www.provideocoalition.com/color-management-part-11-introducing-opencolorio/

     

    OpenColorIO (OCIO) is a new open source project from Sony Imageworks.

     

    Based on development started in 2003, OCIO enables color transforms and image display to be handled in a consistent manner across multiple graphics applications. Unlike other color management solutions, OCIO is geared towards motion-picture post production, with an emphasis on visual effects and animation color pipelines.

     

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    Read more: OpenColorIO standard
  • The Forbidden colors – Red-Green & Blue-Yellow: The Stunning Colors You Can’t See

    www.livescience.com/17948-red-green-blue-yellow-stunning-colors.html

     

     

    While the human eye has red, green, and blue-sensing cones, those cones are cross-wired in the retina to produce a luminance channel plus a red-green and a blue-yellow channel, and it’s data in that color space (known technically as “LAB”) that goes to the brain. That’s why we can’t perceive a reddish-green or a yellowish-blue, whereas such colors can be represented in the RGB color space used by digital cameras.

     

    https://en.rockcontent.com/blog/the-use-of-yellow-in-data-design

    The back of the retina is covered in light-sensitive neurons known as cone cells and rod cells. There are three types of cone cells, each sensitive to different ranges of light. These ranges overlap, but for convenience the cones are referred to as blue (short-wavelength), green (medium-wavelength), and red (long-wavelength). The rod cells are primarily used in low-light situations, so we’ll ignore those for now.

     

    When light enters the eye and hits the cone cells, the cones get excited and send signals to the brain through the visual cortex. Different wavelengths of light excite different combinations of cones to varying levels, which generates our perception of color. You can see that the red cones are most sensitive to light, and the blue cones are least sensitive. The sensitivity of green and red cones overlaps for most of the visible spectrum.

     

    Here’s how your brain takes the signals of light intensity from the cones and turns it into color information. To see red or green, your brain finds the difference between the levels of excitement in your red and green cones. This is the red-green channel.

     

    To get “brightness,” your brain combines the excitement of your red and green cones. This creates the luminance, or black-white, channel. To see yellow or blue, your brain then finds the difference between this luminance signal and the excitement of your blue cones. This is the yellow-blue channel.

     

    From the calculations made in the brain along those three channels, we get four basic colors: blue, green, yellow, and red. Seeing blue is what you experience when low-wavelength light excites the blue cones more than the green and red.

     

    Seeing green happens when light excites the green cones more than the red cones. Seeing red happens when only the red cones are excited by high-wavelength light.

     

    Here’s where it gets interesting. Seeing yellow is what happens when BOTH the green AND red cones are highly excited near their peak sensitivity. This is the biggest collective excitement that your cones ever have, aside from seeing pure white.

     

    Notice that yellow occurs at peak intensity in the graph to the right. Further, the lens and cornea of the eye happen to block shorter wavelengths, reducing sensitivity to blue and violet light.

    Read more: The Forbidden colors – Red-Green & Blue-Yellow: The Stunning Colors You Can’t See
  • No one could see the colour blue until modern times

    https://www.businessinsider.com/what-is-blue-and-how-do-we-see-color-2015-2

    The way that humans see the world… until we have a way to describe something, even something so fundamental as a colour, we may not even notice that something it’s there.

     

    Ancient languages didn’t have a word for blue — not Greek, not Chinese, not Japanese, not Hebrew, not Icelandic cultures. And without a word for the colour, there’s evidence that they may not have seen it at all.

    https://www.wnycstudios.org/story/211119-colors

     

    Every language first had a word for black and for white, or dark and light. The next word for a colour to come into existence — in every language studied around the world — was red, the colour of blood and wine.

    After red, historically, yellow appears, and later, green (though in a couple of languages, yellow and green switch places). The last of these colours to appear in every language is blue.

     

    The only ancient culture to develop a word for blue was the Egyptians — and as it happens, they were also the only culture that had a way to produce a blue dye.

    https://mymodernmet.com/shades-of-blue-color-history/



    https://www.msn.com/en-us/news/technology/scientists-recreate-lost-recipes-for-a-5-000-year-old-egyptian-blue-dye/ar-AA1FXcj1

    Assessment of process variability and color in synthesized and ancient Egyptian blue pigments | npj Heritage Science

    The approximately 5,000-year-old dye wasn’t a single color, but instead encompassed a range of hues, from deep blues to duller grays and greens. Artisans first crafted Egyptian blue during the Fourth Dynasty (roughly 2613 to 2494 BCE) from recipes reliant on calcium-copper silicate. These techniques were later adopted by Romans in lieu of more expensive materials like lapis lazuli and turquoise. But the additional ingredient lists were lost to history by the time of the Renaissance. 

    McCloy’s team confirmed that cuprorivaite—the naturally occurring mineral equivalent to Egyptian blue—remains the primary color influence in each hue. Despite the presence of other components, Egyptian blue appears as a uniform color after the cuprorivaite becomes encased in colorless particles such as silicate during the heating process.

     

    Considered to be the first ever synthetically produced color pigment, Egyptian blue (also known as cuprorivaite) was created around 2,200 B.C. It was made from ground limestone mixed with sand and a copper-containing mineral, such as azurite or malachite, which was then heated between 1470 and 1650°F. The result was an opaque blue glass which then had to be crushed and combined with thickening agents such as egg whites to create a long-lasting paint or glaze.

     

     

    If you think about it, blue doesn’t appear much in nature — there aren’t animals with blue pigments (except for one butterfly, Obrina Olivewing, all animals generate blue through light scattering), blue eyes are rare (also blue through light scattering), and blue flowers are mostly human creations. There is, of course, the sky, but is that really blue?

     

     

    So before we had a word for it, did people not naturally see blue? Do you really see something if you don’t have a word for it?

     

    A researcher named Jules Davidoff traveled to Namibia to investigate this, where he conducted an experiment with the Himba tribe, who speak a language that has no word for blue or distinction between blue and green. When shown a circle with 11 green squares and one blue, they couldn’t pick out which one was different from the others.

     

    When looking at a circle of green squares with only one slightly different shade, they could immediately spot the different one. Can you?

     

    Davidoff says that without a word for a colour, without a way of identifying it as different, it’s much harder for us to notice what’s unique about it — even though our eyes are physically seeing the blocks it in the same way.

     

    Further research brought to wider discussions about color perception in humans. Everything that we make is based on the fact that humans are trichromatic. The television only has 3 colors. Our color printers have 3 different colors. But some people, and in specific some women seemed to be more sensible to color differences… mainly because they’re just more aware or – because of the job that they do.

    Eventually this brought to the discovery of a small percentage of the population, referred to as tetrachromats, which developed an extra cone sensitivity to yellow, likely due to gene modifications.

    The interesting detail about these is that even between tetrachromats, only the ones that had a reason to develop, label and work with extra color sensitivity actually developed the ability to use their native skills.

     

    So before blue became a common concept, maybe humans saw it. But it seems they didn’t know they were seeing it.

    If you see something yet can’t see it, does it exist? Did colours come into existence over time? Not technically, but our ability to notice them… may have…

     

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    Read more: No one could see the colour blue until modern times
  • If a blind person gained sight, could they recognize objects previously touched?

    news.psu.edu/story/141360/2006/04/17/research/probing-question-if-blind-person-gained-sight-could-they-recognize

     

    Blind people who regain their sight may find themselves in a world they don’t immediately comprehend. “It would be more like a sighted person trying to rely on tactile information,” Moore says.

     

    Learning to see is a developmental process, just like learning language, Prof Cathleen Moore continues. “As far as vision goes, a three-and-a-half year old child is already a well-calibrated system.”

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    Read more: If a blind person gained sight, could they recognize objects previously touched?
  • PBR Color Reference List for Materials – by Grzegorz Baran

    The list should be helpful for every material artist who work on PBR materials as it contains over 200 color values measured with PCE-RGB2 1002 Color Spectrometer device and presented in linear and sRGB (2.2) gamma space.

    All color values, HUE and Saturation in this list come from measurements taken with PCE-RGB2 1002 Color Spectrometer device and are presented in linear and sRGB (2.2) gamma space (more info at the end of this video) I calculated Relative Luminance and Luminance values based on captured color using my own equation which takes color based luminance perception into consideration. Bare in mind that there is no ‘one’ color per substance as nothing in nature is even 100% uniform and any value in +/-10% range from these should be considered as correct one. Therefore this list should be always considered as a color reference for material’s albedos, not ulitimate and absolute truth.

     

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    Read more: PBR Color Reference List for Materials – by Grzegorz Baran
  • Practical Aspects of Spectral Data and LEDs in Digital Content Production and Virtual Production – SIGGRAPH 2022

     

    Comparison to the commercial side

     

    https://www.ecolorled.com/blog/detail/what-is-rgb-rgbw-rgbic-strip-lights

     

    RGBW (RGB + White) LED strip uses a 4-in-1 LED chip made up of red, green, blue, and white.

     

    RGBWW (RGB + White + Warm White) LED strip uses either a 5-in-1 LED chip with red, green, blue, white, and warm white for color mixing. The only difference between RGBW and RGBWW is the intensity of the white color. The term RGBCCT consists of RGB and CCT. CCT (Correlated Color Temperature) means that the color temperature of the led strip light can be adjusted to change between warm white and white. Thus, RGBWW strip light is another name of RGBCCT strip.

     

    RGBCW is the acronym for Red, Green, Blue, Cold, and Warm. These 5-in-1 chips are used in supper bright smart LED lighting products

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    Read more: Practical Aspects of Spectral Data and LEDs in Digital Content Production and Virtual Production – SIGGRAPH 2022
  • About green screens

    hackaday.com/2015/02/07/how-green-screen-worked-before-computers/

     

    www.newtek.com/blog/tips/best-green-screen-materials/

     

    www.chromawall.com/blog//chroma-key-green

     

     

    Chroma Key Green, the color of green screens is also known as Chroma Green and is valued at approximately 354C in the Pantone color matching system (PMS).

     

    Chroma Green can be broken down in many different ways. Here is green screen green as other values useful for both physical and digital production:

     

    Green Screen as RGB Color Value: 0, 177, 64
    Green Screen as CMYK Color Value: 81, 0, 92, 0
    Green Screen as Hex Color Value: #00b140
    Green Screen as Websafe Color Value: #009933

     

    Chroma Key Green is reasonably close to an 18% gray reflectance.

     

    Illuminate your green screen with an uniform source with less than 2/3 EV variation.
    The level of brightness at any given f-stop should be equivalent to a 90% white card under the same lighting.

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    Read more: About green screens

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