Gloss, haze, and colour are all optical measurements made on a surface or material, all reported as a single number or set of numbers, and all easy to confuse when you're specifying test equipment for the first time. They measure genuinely different physical properties, and mixing them up leads to buying the wrong instrument for the job.
Gloss — How Much Light Reflects at the Mirror Angle
Gloss measures how much light reflects specularly (at the mirror angle) off a surface, compared to a calibrated reference standard, reported in gloss units (GU) at a specified measurement angle (commonly 20°, 60°, or 85°). A high-gloss surface reflects most incident light at the mirror angle; a matte surface scatters it diffusely instead. Gloss meters are used for surface-finish QC on coatings, plastics, paints, and metals — verifying a finish matches its intended specification, whether that's a high-gloss automotive clearcoat or a deliberately matte plastic housing.
Haze — How Much Light Scatters Near the Direct Transmission Path
Haze measures the percentage of transmitted light that scatters away from the direct path through a transparent or translucent material, expressed as a percentage. A material can have excellent total light transmission and still have high haze — meaning the light passes through but is diffused, reducing image clarity when looking through the material. Haze meters are used for optical clarity QC on films, sheets, lenses, and any transparent or translucent material where clarity (not just transmission percentage) matters.
Colour — The Spectral Composition of Reflected or Transmitted Light
Colour measurement characterises the spectral composition of light reflected from or transmitted through a sample, typically reported in a standardised colour space (CIE L*a*b*, CIE XYZ) that allows numerical comparison and pass/fail tolerance (ΔE) against a reference sample. Colorimeters and spectrophotometers both measure colour, differing mainly in how they capture the underlying spectral data — a colorimeter uses filtered photodetectors approximating the eye's colour response, while a spectrophotometer captures a full spectral curve, generally with higher accuracy and more analytical flexibility.
Choosing Between the Three
| What you're actually checking | Right measurement |
|---|---|
| Does this coating/paint finish match spec (shiny vs matte) | Gloss |
| Is this transparent film/sheet clear enough for its application | Haze |
| Does this material's colour match a reference sample | Colorimeter or spectrophotometer |
| Full spectral transmittance/reflectance profile for R&D | Spectrophotometer |