4 ms·

The WCAG contrast formula is really not great, and gives very misleading results in plenty of situations.

• mark-r 5y ago
  I've wondered where they came up with their formula, because it's not obvious and the results are so clearly wrong in many simple cases. The best I can figure is that they just re-worked some some formula from back in the green-screen CRT days and it's just laughably inappropriate now.
  • tshaddox 5y ago
    It's tough to find any solid info on the actual history of the development of the WCAG contrast criterion, but it looks like they chose to base their concepts on the work done in the mid to late 1990s on the sRGB color space, which itself seems to have been motivated by the desire to maintain the simplicity of defining colors by R, G, and B. The WCAG's "relative luminance" is calculated from the raw RGB values using very simple arithmetic, which tends to not be the case for perceptual color spaces.
    • mark-r 5y ago
      There's definitely an element of sRGB in there, but it feels grafted on to something older. Like someone was tasked with throwing something together from whatever references they could find. P.S. sRGB was motivated by a desire to quantify the behavior of an "average" CRT monitor, and while it probably didn't accomplish that at least it gave everybody a target so that hardware could converge on something sensible.