Do you have any tricks for conforming to APCA when you need to keep track of font weight, font size, and background vs foreground color while designing/developing UIs?
I don't, as for us we set our goal to have a contrast of >60 regardless of font size/weight. Since we already weren't compliant with our 11px font sizes, we chose to use the contrast guidelines without the font size guidelines. Agree it's a lot to manage - we didn't find a great way to solve for this, which is why we mixed and matched WCAG, APCA, and general UX principles rather than relying on a single set of rules.
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
> I don't, as for us we set our goal to have a contrast of >60 regardless of font size/weight.
That's my general strategy too e.g. I'd rather pick a single blue that always works for large and small text, rather than having to keep track of and workaround which shade to use for different sizes.
I do wonder if they'll make some compromises to APCA in this area to make it easier to apply before it's standardised, as there's much more to track now compared to WCAG.
Hi @seanwilson, standards work is nothing BUT compromises it seems.
The reason for the public beta is to find concerns like these.
One of the aspects of APCA that is unique are the many use-case levels that improve design flexibility by focusing contrast values where they are actually needed.
I don't, as for us we set our goal to have a contrast of >60 regardless of font size/weight. Since we already weren't compliant with our 11px font sizes, we chose to use the contrast guidelines without the font size guidelines. Agree it's a lot to manage - we didn't find a great way to solve for this, which is why we mixed and matched WCAG, APCA, and general UX principles rather than relying on a single set of rules.