COLOR

  • 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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  • 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
  • What Is The Resolution and view coverage Of The human Eye. And what distance is TV at best?

    https://www.discovery.com/science/mexapixels-in-human-eye

    About 576 megapixels for the entire field of view.

     

    Consider a view in front of you that is 90 degrees by 90 degrees, like looking through an open window at a scene. The number of pixels would be:
    90 degrees * 60 arc-minutes/degree * 1/0.3 * 90 * 60 * 1/0.3 = 324,000,000 pixels (324 megapixels).

     

    At any one moment, you actually do not perceive that many pixels, but your eye moves around the scene to see all the detail you want. But the human eye really sees a larger field of view, close to 180 degrees. Let’s be conservative and use 120 degrees for the field of view. Then we would see:

    120 * 120 * 60 * 60 / (0.3 * 0.3) = 576 megapixels.

    Or.

    7 megapixels for the 2 degree focus arc… + 1 megapixel for the rest.

    https://clarkvision.com/articles/eye-resolution.html

     

    Details in the post

    (more…)

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  • Sensitivity of human eye

    http://www.wikilectures.eu/index.php/Spectral_sensitivity_of_the_human_eye

     

    http://www.normankoren.com/Human_spectral_sensitivity_small.jpg

     

    Spectral sensitivity of eye is influenced by light intensity. And the light intensity determines the level of activity of cones cell and rod cell. This is the main characteristic of human vision. Sensitivity to individual colors, in other words, wavelengths of the light spectrum, is explained by the RGB (red-green-blue) theory. This theory assumed that there are three kinds of cones. It’s selectively sensitive to red (700-630 nm), green (560-500 nm), and blue (490-450 nm) light. And their mutual interaction allow to perceive all colors of the spectrum.

     

    http://weeklysciencequiz.blogspot.com/2013/01/violet-skies-are-for-birds.html

     

     

    Sensitivity of human eye Sensitivity of human eyes to light increase with the decrease in light intensity. In day-light condition, the cones cell is responding to this condition. And the eye is most sensitive at 555 nm. In darkness condition, the rod cell is responding to this condition. And the eye is most sensitive at 507 nm.

     

    As light intensity decreases, cone function changes more effective way. And when decrease the light intensity, it prompt to accumulation of rhodopsin. Furthermore, in activates rods, it allow to respond to stimuli of light in much lower intensity.

     

    https://www.nde-ed.org/EducationResources/CommunityCollege/PenetrantTest/Introduction/lightresponse.htm

    The three curves in the figure above shows the normalized response of an average human eye to various amounts of ambient light. The shift in sensitivity occurs because two types of photoreceptors called cones and rods are responsible for the eye’s response to light. The curve on the right shows the eye’s response under normal lighting conditions and this is called the photopic response. The cones respond to light under these conditions.

     

    As mentioned previously, cones are composed of three different photo pigments that enable color perception. This curve peaks at 555 nanometers, which means that under normal lighting conditions, the eye is most sensitive to a yellowish-green color. When the light levels drop to near total darkness, the response of the eye changes significantly as shown by the scotopic response curve on the left. At this level of light, the rods are most active and the human eye is more sensitive to the light present, and less sensitive to the range of color. Rods are highly sensitive to light but are comprised of a single photo pigment, which accounts for the loss in ability to discriminate color. At this very low light level, sensitivity to blue, violet, and ultraviolet is increased, but sensitivity to yellow and red is reduced. The heavier curve in the middle represents the eye’s response at the ambient light level found in a typical inspection booth. This curve peaks at 550 nanometers, which means the eye is most sensitive to yellowish-green color at this light level. Fluorescent penetrant inspection materials are designed to fluoresce at around 550 nanometers to produce optimal sensitivity under dim lighting conditions.

     

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  • 3D Lighting Tutorial by Amaan Kram

    http://www.amaanakram.com/lightingT/part1.htm

    The goals of lighting in 3D computer graphics are more or less the same as those of real world lighting.

     

    Lighting serves a basic function of bringing out, or pushing back the shapes of objects visible from the camera’s view.
    It gives a two-dimensional image on the monitor an illusion of the third dimension-depth.

    But it does not just stop there. It gives an image its personality, its character. A scene lit in different ways can give a feeling of happiness, of sorrow, of fear etc., and it can do so in dramatic or subtle ways. Along with personality and character, lighting fills a scene with emotion that is directly transmitted to the viewer.

     

    Trying to simulate a real environment in an artificial one can be a daunting task. But even if you make your 3D rendering look absolutely photo-realistic, it doesn’t guarantee that the image carries enough emotion to elicit a “wow” from the people viewing it.

     

    Making 3D renderings photo-realistic can be hard. Putting deep emotions in them can be even harder. However, if you plan out your lighting strategy for the mood and emotion that you want your rendering to express, you make the process easier for yourself.

     

    Each light source can be broken down in to 4 distinct components and analyzed accordingly.

    · Intensity
    · Direction
    · Color
    · Size

     

    The overall thrust of this writing is to produce photo-realistic images by applying good lighting techniques.

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    Read more: 3D Lighting Tutorial by Amaan Kram
  • Tim Kang – calibrated white light values in sRGB color space

    https://www.linkedin.com/posts/timkang_colorimetry-cinematography-nerdalert-activity-7058330978007584769-9xln

     

    8bit sRGB encoded
    2000K 255 139 22
    2700K 255 172 89
    3000K 255 184 109
    3200K 255 190 122
    4000K 255 211 165
    4300K 255 219 178
    D50 255 235 205
    D55 255 243 224
    D5600 255 244 227
    D6000 255 249 240
    D65 255 255 255
    D10000 202 221 255
    D20000 166 196 255

    8bit Rec709 Gamma 2.4
    2000K 255 145 34
    2700K 255 177 97
    3000K 255 187 117
    3200K 255 193 129
    4000K 255 214 170
    4300K 255 221 182
    D50 255 236 208
    D55 255 243 226
    D5600 255 245 229
    D6000 255 250 241
    D65 255 255 255
    D10000 204 222 255
    D20000 170 199 255

    8bit Display P3 encoded
    2000K 255 154 63
    2700K 255 185 109
    3000K 255 195 127
    3200K 255 201 138
    4000K 255 219 176
    4300K 255 225 187
    D50 255 239 212
    D55 255 245 228
    D5600 255 246 231
    D6000 255 251 242
    D65 255 255 255
    D10000 208 223 255
    D20000 175 199 255

    10bit Rec2020 PQ (100 nits)
    2000K 520 435 273
    2700K 520 466 358
    3000K 520 475 384
    3200K 520 480 399
    4000K 520 495 446
    4300K 520 500 458
    D50 520 510 482
    D55 520 514 497
    D5600 520 514 500
    D6000 520 517 509
    D65 520 520 520
    D10000 479 489 520
    D20000 448 464 520

     

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    Read more: Tim Kang – calibrated white light values in sRGB color space

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