Graininess

Graininess describes how coarse or fine an effect coating appears under diffuse viewing conditions, similar to looking at a panel outside on a cloudy day when the light is spread evenly across the sky. In this situation and the underlying flake texture of the coating becomes more visible than sharp, directional sparkle from the metallic particles.

What Graininess represents

• Graininess quantifies the low‑frequency mottling or speckle pattern caused by non-uniform flake distribution and local brightness variations across the surface that are most apparent under diffuse conditions.
• Higher Graininess values indicate a more visibly textured, patchy or “noisy” effect, while lower values indicate a more uniform, fine and homogeneous finish.

How Graininess is measured

• The parameter is derived from the spatial variation in reflected intensity within the measured area, using data from all six illumination directions and processing it to remove specular contributions from the sparkling elements.

How to use Graininess in practice

• Use Graininess, referenced to diffuse viewing conditions (cloudy‑day type lighting), to set and check appearance specifications for metallic and pearlescent coatings, ensuring that production parts match master panels in perceived coarseness under typical daylight, showroom or indoor lighting.
• Compare Graininess alongside sparkle metrics and waviness to separate diffuse‑appearance texture issues (e.g. layout, flocculation) from directional sparkle behaviour when diagnosing or optimising effect coatings.

Technical specification