Why colors match indoors but not in daylight — Metamerism

Two fabric swatches look identical under store lighting but clearly different in daylight. Nobody's eyes are wrong — it's a physical phenomenon called metamerism.

Different dyes reflect the light spectrum differently. Two samples may reflect identical light into your eyes under one illuminant (e.g. TL84 store fluorescent) yet diverge under another (D65 daylight or incandescent A). Color is not an intrinsic property — it is the product of illuminant × reflectance × observer.

What this means for textile production

• Always agree on the illuminant: the industry judges primarily under D65, often cross-checking TL84 and A.
• Assess color in a standard light booth, not under office lights or by a window.
• Screens (including this site) are approximations — physical swatches and sealed samples prevail.
• When re-dyeing with different dyes or substrates, re-check under multiple illuminants even if ΔE is small.

Share this page with clients to explain why inspections require an agreed illuminant and sealed physical samples.