Color notes - references, links, and unsorted stuff

From Helpful
Jump to: navigation, search
The physical and human spects dealing with audio, video, and images

Vision and color perception: objectively describing color · the eyes and the brain · physics, numbers, and (non)linearity · color spaces · references, links, and unsorted stuff

Audio physics and physiology: Basic sound physics · Human hearing, psychoacoustics · Descriptions used for sound and music

Digital sound and processing: capture, storage, reproduction · programming and codescs · some glossary · Audio and signal processing - unsorted stuff

Image: file formats · image processing

Video: format notes · encoding notes

Noise stuff: Stray signals and noise · sound-related noise names · electronic non-coupled noise names · electronic coupled noise · ground loop · strategies to avoid coupled noise · Sampling, reproduction, and transmission distortions

Unsorted: Signal analysis, modeling, processing (some audio, some more generic)

For more, see Category:Audio, video, images


Grayscale conversion from RGB

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

The easiest conversion to grayscale is a simple average, (r+g+b)/3, but this is not very perception-accurate.

There are various RGB standards that mention grayscale conversion as weighing of the channels. In some cases this is based on perception, in some it correction for RGB primaries used in the standard (probably based on phosphors?).

These include:

  • ITU-601-1 and a few others use nearly identical numbers, 0.298954*R + 0.586434*G + 0.114612*B (apparently originating from CIE-XYZ 1931(verify))
  • EBU/ITU 3213 (PAL(verify))): 0.222*R + 0.707*G + 0.071*B
  • BT/ITU-709 (NTSC(verify))): 0.213*R + 0.715*G + 0.072*B
  • ...more

The best choice depends mostly on what sort of RGB you have.

It can also depend on specicic wishes. Consider how photographers sometimes use specific colored lenses (or nearly-equivalent photoshop filters) for specific effects, such as lessening the visibility of freckles, making skies more contrasted, and such.

Undetailed so far

Mostly colour spaces, colour models, and transforms. Again, these are not necessarily accurate.

  • HSV, HSB, HSL/HLS, HSI - hue, saturation, and brightness/level/luminisity/intensity. * IHS,
  • YUV, YIQ, YCbCr
  • HMMD
  • StW, I1I2I3
  • Retinal Cone
  • Munsell
  • Karhonen-Loeve

And things I've read about them:

  • NTSC RGB seems to refer to the defined conversion from YIQ to RGB inside the TV.
  • SMPTE RGB apparently does the same but matches modern phosphors better.
  • IHS conversions seems inconsistently defined between books.
  • I1I2I3 is defined from an (unspecified?) RGB as I1=(R+G+B)/3, I2=(R-B)/2, I3=(2G-R-B)/4, so seems to be a luminance-and-opposite type of system.
  • CIE L*a*b* apparently agrees with Munsell's colour system well.

File format notes:

  • GIF stores RGB
  • JPG stores RGB, YCbCr, or CMYK (verify)
  • PNG is RGB (sRGB unless it stores an ICC profile)

Web gamma:

References and other links



CIE stuff






Online calculators

Color pickers

Color pickers / color schemes / color coordination, often for styles

Social scheming

Reference lists


(considering color blindness and such):


More links: