Model Box measurement session 2026-09-18
X-Rite ColorMunki Photo via ArgyllCMS, reflective 45/0, M2, calibrated on the internal tile.
The 19 cards used in the blog post, on mini European cards.

Each card was read at ten spots, the head lifted and moved between every reading. A card's value is
the mean of the three spots whose colour lies farthest from the bare card stock, which was measured
blank in the same session and is in substrate.csv: a thin spot reads as a mixture of paint and card,
so the spots farthest from the card are the ones where the film hid it. The spread among those three
(the `span` column) is the coverage flag: under 0.20 the card bottomed out, over 0.40 the film is
thin and the value is a limit rather than a measurement.

This archive carries the three valued spots of each card, 57 spectra in all -- enough to
recompute every number the post prints, for any illuminant or observer. The remaining spots of each
card are not published.

cards.csv           one row per card: paint, lot, purchase date, painting time, read time, coats, thinner, notes
spectra/*.sp        ArgyllCMS spectral files, one per spot (brand_code_spot.sp), 380-730 nm in 10 nm steps,
                    reflectance in percent; the instrument is specified for 400-700 nm, treat the outer bands as unreliable
measured.csv        CIELAB (D50, 2 degree observer) per spot, from spec2cie
measured-oklab.csv  OKLab (D65) per spot, the unit Model Box ranks matches in (multiply by 100 for the app's dE)
summary.csv         the card values in both spaces, with span, pull and the distance to the substrate
substrate.csv       the blank card of the same stock, the reference the values are computed against

Blog post: https://modelbox.pl/en/blog/color-charts-are-artwork/

License: CC BY-NC-SA 4.0, https://creativecommons.org/licenses/by-nc-sa/4.0/
Attribution: Model Box (https://modelbox.pl), measurement session 2026-09-18.
Non-commercial use only; share derived data under the same license.
