Guides
Longer explanations behind the tools. Each guide is built on numbers we computed ourselves and says how.
- Substituting DMC floss: why charts disagree, and how to pick a swap that holds up
Open DMC color lists come from two sources that differ by a median ΔE of 6.9, and they agree on the nearest substitute for only 17% of threads.
- Pantone to HEX: why every site gives a different code
Four open Pantone lists agree within ΔE 3 for only 22% of codes, and 21% of coated inks have no exact HEX at all.
· updated - How color-blind people see, and how far to trust a simulator
Three color-blindness models agree on which colors merge for red-green types and disagree for blue-yellow; skipping one decoding step moves colors by up to ΔE 40.
- How vision evolved: from a light-sensing cell to the human eye
One photo through eight stages of eye evolution, in ten pictures from archaea to the human eye, with the angles from published studies: one brightness value, a direction, 25° patches, a trilobite’s compound eye, a pinhole blur, then color.
- How many colors can the human eye see? We counted the ones your screen can show
The best-known estimates run from 1 to 40 million, and the earliest source we found for the famous 10 million is one sentence from 1939. Of the 16.7 million screen codes, about 110,000–250,000 stay a just-noticeable step apart.
- Tetrachromacy: who has a fourth cone, and why no online test can find it
About 12% of women carry genes for a fourth cone type, but in the main study only 1 of 24 carriers saw an extra dimension of color. A screen has three primaries, so it cannot test for it.
- The Purkinje effect: why reds go dark at dusk and blues stay bright
At night the eye switches from cones to rods and its peak sensitivity moves from 555 to 507 nm. Computed from the CIE tables: by day a red is about 3 times as bright as a blue, at night the blue is 22 times as bright as the red.
- What is CRI? How colors look under LED, fluorescent and sodium lamps
Computed from CIE lamp spectra: a typical warm white LED scores Ra 82 but only 13 on saturated red (R9), a warm LED with a red chip 92, a violet-pumped LED 96, a sodium street lamp 8.
- APCA vs WCAG 2: what Lc means and where the two contrast methods disagree
WCAG 2’s 4.5:1 is the contrast test laws cite; APCA’s Lc is a beta method that adds font size and weight. Computed with the apca-w3 package: the two pick a different text color on 28% of backgrounds.