COLOR

  • Capturing textures albedo

    Building a Portable PBR Texture Scanner by Stephane Lb
    http://rtgfx.com/pbr-texture-scanner/

     

     

    How To Split Specular And Diffuse In Real Images, by John Hable
    http://filmicworlds.com/blog/how-to-split-specular-and-diffuse-in-real-images/

     

    Capturing albedo using a Spectralon
    https://www.activision.com/cdn/research/Real_World_Measurements_for_Call_of_Duty_Advanced_Warfare.pdf

    Real_World_Measurements_for_Call_of_Duty_Advanced_Warfare.pdf

    Spectralon is a teflon-based pressed powderthat comes closest to being a pure Lambertian diffuse material that reflects 100% of all light. If we take an HDR photograph of the Spectralon alongside the material to be measured, we can derive thediffuse albedo of that material.

     

    The process to capture diffuse reflectance is very similar to the one outlined by Hable.

     

    1. We put a linear polarizing filter in front of the camera lens and a second linear polarizing filterin front of a modeling light or a flash such that the two filters are oriented perpendicular to eachother, i.e. cross polarized.

     

    2. We place Spectralon close to and parallel with the material we are capturing and take brack-eted shots of the setup7. Typically, we’ll take nine photographs, from -4EV to +4EV in 1EVincrements.

     

    3. We convert the bracketed shots to a linear HDR image. We found that many HDR packagesdo not produce an HDR image in which the pixel values are linear. PTGui is an example of apackage which does generate a linear HDR image. At this point, because of the cross polarization,the image is one of surface diffuse response.

     

    4. We open the file in Photoshop and normalize the image by color picking the Spectralon, filling anew layer with that color and setting that layer to “Divide”. This sets the Spectralon to 1 in theimage. All other color values are relative to this so we can consider them as diffuse albedo.

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  • Black Body color aka the Planckian Locus curve for white point eye perception

    http://en.wikipedia.org/wiki/Black-body_radiation

     

    Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body (an opaque and non-reflective body) held at constant, uniform temperature. The radiation has a specific spectrum and intensity that depends only on the temperature of the body.

     

    A black-body at room temperature appears black, as most of the energy it radiates is infra-red and cannot be perceived by the human eye. At higher temperatures, black bodies glow with increasing intensity and colors that range from dull red to blindingly brilliant blue-white as the temperature increases.

    The Black Body Ultraviolet Catastrophe Experiment

     

    In photography, color temperature describes the spectrum of light which is radiated from a “blackbody” with that surface temperature. A blackbody is an object which absorbs all incident light — neither reflecting it nor allowing it to pass through.

     

    The Sun closely approximates a black-body radiator. Another rough analogue of blackbody radiation in our day to day experience might be in heating a metal or stone: these are said to become “red hot” when they attain one temperature, and then “white hot” for even higher temperatures. Similarly, black bodies at different temperatures also have varying color temperatures of “white light.”

     

    Despite its name, light which may appear white does not necessarily contain an even distribution of colors across the visible spectrum.

     

    Although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is used as a first approximation for the energy they emit. Black holes are near-perfect black bodies, and it is believed that they emit black-body radiation (called Hawking radiation), with a temperature that depends on the mass of the hole.

     

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  • Colour – MacBeth Chart Checker Detection

    github.com/colour-science/colour-checker-detection

    A Python package implementing various colour checker detection algorithms and related utilities.

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  • OLED vs QLED – What TV is better?

     

    Supported by LG, Philips, Panasonic and Sony sell the OLED system TVs.
    OLED stands for “organic light emitting diode.”
    It is a fundamentally different technology from LCD, the major type of TV today.
    OLED is “emissive,” meaning the pixels emit their own light.

     

    Samsung is branding its best TVs with a new acronym: “QLED”
    QLED (according to Samsung) stands for “quantum dot LED TV.”
    It is a variation of the common LED LCD, adding a quantum dot film to the LCD “sandwich.”
    QLED, like LCD, is, in its current form, “transmissive” and relies on an LED backlight.

     

    OLED is the only technology capable of absolute blacks and extremely bright whites on a per-pixel basis. LCD definitely can’t do that, and even the vaunted, beloved, dearly departed plasma couldn’t do absolute blacks.

    QLED, as an improvement over OLED, significantly improves the picture quality. QLED can produce an even wider range of colors than OLED, which says something about this new tech. QLED is also known to produce up to 40% higher luminance efficiency than OLED technology. Further, many tests conclude that QLED is far more efficient in terms of power consumption than its predecessor, OLED.

     

    When analyzing TVs color, it may be beneficial to consider at least 3 elements:
    “Color Depth”, “Color Gamut”, and “Dynamic Range”.

     

    Color Depth (or “Bit-Depth”, e.g. 8-bit, 10-bit, 12-bit) determines how many distinct color variations (tones/shades) can be viewed on a given display.

     

    Color Gamut (e.g. WCG) determines which specific colors can be displayed from a given “Color Space” (Rec.709, Rec.2020, DCI-P3) (i.e. the color range).

     

    Dynamic Range (SDR, HDR) determines the luminosity range of a specific color – from its darkest shade (or tone) to its brightest.

     

    The overall brightness range of a color will be determined by a display’s “contrast ratio”, that is, the ratio of luminance between the darkest black that can be produced and the brightest white.

     

    Color Volume is the “Color Gamut” + the “Dynamic/Luminosity Range”.
    A TV’s Color Volume will not only determine which specific colors can be displayed (the color range) but also that color’s luminosity range, which will have an affect on its “brightness”, and “colorfulness” (intensity and saturation).

     

    The better the colour volume in a TV, the closer to life the colours appear.

     

    QLED TV can express nearly all of the colours in the DCI-P3 colour space, and of those colours, express 100% of the colour volume, thereby producing an incredible range of colours.

     

    With OLED TV, when the image is too bright, the percentage of the colours in the colour volume produced by the TV drops significantly. The colours get washed out and can only express around 70% colour volume, making the picture quality drop too.

     

    Note. OLED TV uses organic material, so it may lose colour expression as it ages.

     

    Resources for more reading and comparison below

    www.avsforum.com/forum/166-lcd-flat-panel-displays/2812161-what-color-volume.html

     

    www.newtechnologytv.com/qled-vs-oled/

     

    news.samsung.com/za/qled-tv-vs-oled-tv

     

    www.cnet.com/news/qled-vs-oled-samsungs-tv-tech-and-lgs-tv-tech-are-not-the-same/

     

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