File Formats

Four ways out of the library, and they are not interchangeable. Two carry the spectrum and two do not — which decides what the receiving system can still work out for itself.

Sizes for M2 with spectral data included. Every file is built in your browser when you press Download; nothing is uploaded and nothing is recorded.

CxF — the one to send a supplier

ISO 17972-1. XML, one entry per colour, carrying the full reflectance curve — 36 readings from 380 to 730 nm — alongside the Lab values. Choose All as the measurement condition and it carries M0, M1 and M2 together, each with its own measurement specification, so the receiving system picks the one that matches its workflow.

This is the format that survives the journey. An ink kitchen fed a CxF can aim at the shape of the curve rather than at three numbers, which is what makes a recipe hold up under lights nobody tested — see Metamerism.

CxF/X-4 is a different thing, and we do not ship it

ISO 17972-4 characterises an ink on a substrate: the solid and a ladder of tints, measured over white and over black backing, which is what tells a RIP how the halftones behave and how opaque the ink is.

ChromaSpot is deliberately substrate independent, so there is nothing for it to characterise — the colour is specified before anyone has chosen a material. CxF/X-4 comes later, when a supplier has made the ink and drawn it down on the production stock. The two sit at different points of the same workflow and a good process uses both: One Colour, Many Materials follows it stage by stage.

CGATS TXT

CGATS.17, plain text, tab separated. A header describing what was measured, then one row per sample: id, name, L, a, b, and the 36 spectral readings. Every measurement application in the industry reads it, and you can open it in a text editor and check it by eye, which is not nothing.

One measurement condition per file. Untick Include spectral data and you get the Lab columns alone.

Adobe Color Book — ACB

Installs into Adobe applications and appears in the Swatches panel dropdown beside the libraries that ship with them. Copy the file into the application’s Color Books folder and restart it; the exact location moves between versions.

ACB stores Lab in three bytes — one per channel — so a value is rounded to the nearest of 256 steps. That is a real loss of precision, and it is the format’s, not ours. For a swatch you pick from on screen it is invisible; for a target you hand to a supplier, send CxF.

Adobe Swatch Exchange — ASE

No installation: Swatches panel, then Load Swatches. Lab as 32-bit floating point, so no quantisation, but it lives with the document rather than with the application. Right for a palette on one project, wrong as a permanent library — a few dozen swatches rather than four thousand.

What travels with the file

Every export carries the subset, the measurement condition and any Range filter in its description and its file name, so a file found on a server in six months can still say what it is. What it does not carry is the illuminant and observer you were viewing under — those change the Lab values written into ACB and ASE, so if you have moved away from D50 at 2°, say so when you send the file.