Color Evaluation turns a coating’s spectrum into a perceived color. It takes the reflectance or transmittance across the visible range, weights it by a standard observer and illuminant, and reports where the result sits on the CIE chromaticity diagram along with a color swatch and a full set of color-space values. Use it to predict the visible appearance of a coating — the tint of an antireflection film, the hue of a decorative mirror, or how a filter shifts color with viewing angle.

The spectrum is sampled across 380–780 nm and fed through the standard colorimetric integral, so the color matches the curves shown in Optical Evaluation.

Settings

Characteristic — compute the color of reflected (R) or transmitted (T) light.

Polarization — average, s, or p. Average is the usual choice for unpolarized illumination.

AOI — the viewing angle in degrees. Sweep this to see how an iridescent coating shifts color with incidence.

Observer — the CIE color-matching functions: the 1931 2° observer for small fields or the 1964 10° observer for larger fields.

Illuminant — the light source the color is computed under: daylight (D65, D50), incandescent (A), and equal-energy (E).

Step — the wavelength sampling interval in nm for the color integral. A finer step improves accuracy on coatings with sharp spectral features.

Exposure — the brightness of the color swatch only. By default the swatch is scaled against a perfect white reflector, so a very dim reflection — such as the residual color of a strong antireflection coating — renders almost black even when its hue is highly saturated. Raise the exposure (×10 up to ×1000) or choose Fit hue to rescale the swatch and reveal the hue at full brightness. The numeric readout does not change; only the swatch is re-exposed. This mirrors what the eye sees when the coating reflects a bright source instead of a dim scene.

The evaluation surface (front, back, or total) is set in the Design Editor and shown as a badge on the window.

How to read it

The chromaticity diagram shows the spectral locus (the horseshoe of pure colors), the Planckian white points, and a marker for your coating. A marker near the white point means a near-neutral, colorless coating; a marker pulled toward an edge of the locus means a strong, saturated tint. The swatch renders the same result as an approximate on-screen color.

Because the swatch is referenced to a perfect white reflector, a dim reflection looks dark or black even when the chromaticity marker sits far out toward the locus: the color is genuinely there, but there is little reflected light to carry it. Use the Exposure setting to bring that hue up to a visible brightness without changing the reported values.

The numeric panel reports the full set of standard descriptors: tristimulus X, Y, Z; xy and u′v′ chromaticity; CIE L*a*b* and L*u*v* with their chroma and hue angles; dominant wavelength and purity; and correlated color temperature (CCT) with its offset from the Planckian locus (Duv). For industrial color matching, a color difference of ΔE ≤ 1 is generally taken as the threshold of a just-noticeable difference.

References

• CIE 15:2004 — Colorimetry, 3rd ed.
• Sharma, Wu, Dalal, Color Res. Appl. 30, 21 (2005) — CIEDE2000.
• H. A. Macleod, Thin-Film Optical Filters, 5th ed., §12.2 (Eqs. 12.1–12.5).