[mpetroff]

The WCAG also define the contrast ratio in terms of sRGB, which is not a perceptually-uniform color space. This makes the WCAG contrast ratios somewhat meaningless in terms of human visual perception. It's accessibility by edict, not science.

There's a rather lengthy discussion of this on the WCAG issue tracker [1].

[1] https://github.com/w3c/wcag/issues/695

[nx7487]

The issue creator also points out "It is a concern for me because this W3C document is considered authoritative, and has made its way into government regulations." Pretty interesting thread.

[refulgentis]

hah, awesome, I know exactly what issue this is without clicking through - Myndex is wrong on this, shockingly, but unfortunately my lips have to be sealed, for now.

Look into the correspondence between the space Myndex uses, the space contrast ratio is measured in, and then again at the W3C docs: TL;DR Myndex's approach doesn't account for reflectance off the screen