Measure and Find Colour

You have a physical sample — a print, a swatch, a product — and you want to know which ChromaSpot colour it is. That takes an instrument, and a less expensive one than most people assume.

Why a photograph will not do

A camera records three numbers per pixel, under whatever light happened to be there, filtered by whatever the camera decided about white balance. A screen then shows you those numbers under a different light again.

A spectrophotometer supplies its own light, measures the surface at each wavelength, and reports what the surface does rather than what it looked like at the time. That is the difference between matching a colour and guessing at it — see Light, Spectrum, Observer.

What you need

An instrument	A spectrophotometer. A pocket device is enough to identify a colour; the accuracy that matters here is repeatability, not laboratory calibration.
Software	CC Capture drives most instruments on the market. Its trial mode is free and needs no registration.
A flat sample	Big enough for the aperture, on a stable backing, not curled.

The procedure

Connect and calibrate. Every instrument has its own routine — usually a white tile. Do it; without it the readings are decorative.
Measure. Press the button on the device or in the software.
Open the Designer tab. It reports the nearest ChromaSpot code and the colour difference to it.
Read the difference, not just the code. Under 2.5 and the library has your colour. Above 4 and it does not — the nearest entry is a neighbour, not a match.

One reading is not a measurement

Print is not uniform. Ink lies differently a centimetre away; the substrate varies; the instrument sees a small circle and nothing else.

Use Start Variation. It takes a series of readings as you move the instrument around the sample and reports the average and the spread. The spread is the useful part: a tight one means the sample is uniform and the number can be trusted, and a wide one means the sample itself is inconsistent and no single reading was ever going to represent it.

For scale. Re-reading the same spot without moving the instrument varies by about 0.03 ΔE₀₀. If moving it around the sample gives a spread of 2, that is the print, not the instrument.

Beyond the nearest code

The other tabs answer questions the code alone does not.

CII	How far your sample moves as the light changes — see Colour Inconstancy.
The spectral curve	Compare its shape with the library colour’s. Two colours with the same Lab and different curves will part company under another lamp — Metamerism.
M0 / M1 / M2	If they differ, the substrate has brighteners in it, and by how much — Optical Brighteners.

Finding it without an instrument

If you already have Lab values from somewhere — a specification, a supplier, a measurement report — paste them into the browser’s LAB view and set the mode to ΔE₀₀. A radius of 2.5 shows everything the library considers the same colour.

Check what condition those Lab values were measured under before trusting the answer. D50/2°/M2 is what this library assumes, and a figure measured at 10° or under M1 is answering a different question.