Myndex

There's also a curated linktree of key resources.

https://linktr.ee/Myndex

It will be moving to its own URL soon: apcacontrast.com

That URL works now, as a redirect, but will become the host soon.

My guess here, to help it make sense, perhaps think in terms of the luminous excitation of "blacklight paint"... If she's having strong reactions, probably to metamers under the right lighting in a real-world environment and not constrained by the gamut of a defined colorspace like some flavor of CMYK or RGB...

Here's a real question for her on the subject, how does she see a blacklight? I expect a true tetrachromat to see it nearly white. But also I wonder if she's sensing a fluorescing that is of sufficiently short wavelength that standard vision can not perceive it.

The implants I have in each eye are different technologies. The right eye has no UV filter, the IOL in the left eye does have a UV filter. When I look at a blacklight with my right eye, it's bright, almost white in appearance.

But looking at the blacklight with my left eye, it looks like what most see, as a very dark purple with almost no visible light.

A friend of mine is an artist who has been experimenting with extreme metamerism, using pigments that radically change perceived color under different light sources, including of course, blacklight.

Since you mention hiking, I wonder if some of the plant life you and your wife encounter have any florescent properties, or perhaps interact with some fungus that does... A portable UV light at night might be interesting...

Hey @zauguin and @kreskin,

I am sorry about the licensing issue, it is only temporary during the public beta. And I am providing some exceptions, if you need, send an email to [email protected]

Just can't do an MIT type license right now—and really there's no generic one that really suit what we need right now, so we're working on such a license, one that is reasonably permissive yet prevents some of the issues we've run into. I.e. like with bad actors incorrectly modifying, or reverse engineering and doing so wrongly, or taking it to the cantina at Mos Eisley...

[delayed]

Hi @jjcm and @seanwilson

First of all thank you for these comments, I do proactively seek out comments like these as there are too few at the official APCA discussion forum https://github.com/Myndex/SAPC-APCA/discussions That said:

A px is not a device pixel, it is referenced to the canvas abstraction layer as the canonical CSS reference px. It represents 1.278 arc minutes of visual angle as subtended onto the retina. Or 0.0213° 𝑽𝜽

This is the case with a 96ppi monitor at 28" away.

Visual Angle in arc minutes is what is used in research, and in fact what the Snellen eye chart is based around, 20/20 is based on a capital E that is 5 arc minutes high, where each line is 1 arcmin, and each space between the three horizontal lines is 1 arcmin, where we then find a spatial frequency of 30 cycles per degree.

But that is for minimum acuity .

Minimum acuity is NOT best readability, which needs to be ~2.5 or times larger than the acuity size (critical size). For a standard display a reference distance away, that means an x-height of 9.4px, which is 12 minutes of arc 𝑽𝜽.

Critical size and critical contrast are recited and empirically tested for decades by eminent readability researchers Whittacker, Lovi-Kitchin, Ian Bailey, Legge, et alia.

The font sizes for APCA are based on this, and assuming a reference font like Helvetica with a 0.52 x-height ratio.

ALSO, if you want a "catch all" contrast value,Lc 75 is more appropriate IMO.

NOT SET IN STONE YET

This kind of discussion is good at the forum, so that it can be tracked and considered in the conversations about guidelines.

ALSO

If you want an easy way to use APCA and be fully backwards compatible with the old WCAG 2.x, then try BridgePCA at https://bridgepca.com

WCAG 2.x was neither peer reviewed nor empirically tested—true. However this is not the case for the candidate for WCAG 3, which is APCA. APCA has been in public beta testing for two and a half years, is the subject of ongoing empirical studies, and does already have journal published peer review, as well as independent peer reviews by PhDs, vision scientists, data scientists, and other technologists.

See a partial listing of reviews: https://git.apcacontrast.com/documentation/independent-revie...

The Medium platform has a lot of good features going for it, yet it literally ignores visual accessibility. For a platform that is entirely based around readable content, one would think that it’d be close to State of the Art, instead of the State of Unreadable.

Nate Baldwin (the developer behind Adobe Leonardo) created the site, and did a pretty amazing job, taking an extremely complicated and nuanced topic (color) and breaking it down into small, bite-size pieces for this encyclopedic reference.

Nate developed the site before AI like GPT were available. Color is a very difficult subject—but the site is filled with the references that it's relating to, so if you want the deeper dive, go to those multi-hundred page references.

As far as the guide to contrast, look at the navigation on the left, and go to the contrast section. The site is set up more like an encyclopedic reference as opposed to a read-from-the-top blog.

There is some conflation here between an art definition and the colorimetric definition. In colorimetry:

Luminance is a spectrally weighted measure of physical light, it is not a perception, and luminance is linear to physical light.

Lightness is the perception of luminance, along with darkness and brightness. In colorimetry, the term lightness is used to distinguish the perception of light (which is nonlinear to physical light) as opposed to luminance which is a linear measure of physical light.

Luminance is denoted Y (relative) or L (absolute), Perceptual lightness is L* (Lstar) or J, brightness as Q (in most models).

As you noted, the term lightness can also be used as a tonal metric (i.e. in art). However in colorimetry, the closeness to white, or achromatic, is described as less purity (less chroma or less saturation).

And for the record, the site is not auto-generated. Nate Baldwin created that site. Nate is also the developer behind Adobe Leonardo, the color palette utility.

As for the Helmholtz–Kohlrausch phenomenon, here is the official definition from the CIE - International Commission on Illumination

Change in brightness of perceived colour, produced by increasing the purity of a colour stimulus while keeping its luminance constant within the range of photopic vision

Note 1 to entry: For related colours, a change in lightness can also occur when the purity is increased while keeping the luminance factor of the colour stimulus constant.

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The CIE points out that the change in perceived lightness occurs with increased saturation (purity).

!! Thank you for mentioning... and to add, human perception of contrast is actually driven more by the spatial characteristics (size, weight, thickness) than by the distance between two colors. This is a key reason that contrast measures that consider only the distance between two colors fail at predicting contrast.

Clearing up a few misconceptions regarding color and contrast in design.

Thank you for posting

I can say it has been immensely helpful reading through the comments here and I thank you all for your input. If you want to read further regarding the readability research project, there's a catalog of resources and further articles at:

https://git.myndex.com

Then you missed the key part of the article as nowhere in the article did I ever advocate #fff/#000

Yes often the case

I guess what I wrote about adaptation didn't some across as clearly as I had hoped.

Adapting to the ambient light and reading on paper which is never more than 90% DIFFUSE reflectance (typically 80% for paperbacks, and 70% for newspaper) is not at all like having polarized light beamed straight into your ocular medium to collide with your retina at well over 100% of the ambient adaptation level. Or words to that effect.

> _There is such a thing as too much contrast._

Yes, there is absolutely such a thing as too much contrast, however, I hesitate to say this as it is so often misunderstood—spatial frequency is the key factor to determine first. The contrast needed for small thin body text is very different than that needed for a large bold headline.

The thing that some find confusing is thinking that too much contrast with a light background means making the small thin text lighter grey, when in fact the text should stay darker tha #303030, and lower the luminance of the background to #e6e2dd. I say as much in the article.

NOWHERE, absolutely nowhere in the article did I suggest using #fff/#000

On the contrary, I highly recommend that for light backgrounds the, background directly under body text be something like #e6e2dd. I explain this in the article.

The simple answer is that this one article received tens of thousands of reads in a day. My other sites, not so much,

Medium does not allow the author to set the text color at all.

Try https://www.myndex.com/APCA/

No choice thanks to Medium.

Unfortunately, Medium does not allow setting the text color — they set it automatically based on the background... After trying several combinations, I've mostly given up with that site and am planning on moving to another.

I also use GitHub pages, and other sites, and my own independent sites. But, none get the level of readers — this one article on Medium received tens of thousands of reads. For some of the other materials in teh current research, see the catalog at git.myndex.com

Thank you for reading.

Yea, I do that often.

Medium is lame for more reasons than you might imagine, I have not had the time to move things to another site though. If you want, my catalog of current contrast research resources is listed at git.myndex.com

It's Medium's CMS. Author has no control over the text color, and I've been experimenting with combinations trying to find something useful. An effort in futility. I'm planning on moving my articles to my own site... then... then this went viral. OMG. The true irony.