Lopacità

Lopacité is a term used in some French-language optics discussions to describe a property of materials that quantifies how effectively a medium blocks or retards light, taking into account both absorption and scattering as light diffuses within the material. The concept is relatively new and not yet standardized, and it is often discussed in the context of coatings, textiles, foams, and architectural materials where visual appearance depends on both transmission and diffusion of light.

Definition and scope

In practical use, lopacité is treated as a dimensionless quantity that ranges roughly from 0 to 1. A value near 0 corresponds to a material that allows light to pass through with minimal disturbance (near transparency in the measurement geometry), while a value near 1 indicates a material that is effectively opaque under the same conditions. Unlike simple absorptance or opacity alone, lopacité aims to capture the combined influence of absorption, scattering, and internal diffusion on the appearance of the material.

Measurement approaches

Lopacité is usually inferred from optical measurements that combine transmittance and scattering data. Common techniques include integrating-sphere measurements, diffuse and specular reflectance analyses, and angular-resolved scattering, often under diffuse illumination. The resulting value depends on wavelength, incident angle, and the geometry of the measurement setup, reflecting the non-unique nature of optical diffusion.

Context and usage

The term is used to compare materials where both absorption and scattering govern how light is perceived, providing a compact descriptor for design and quality control in optics, coatings, textiles, and display surfaces. Because lopacité is not yet standardized, practitioners may adopt varying definitions or measurement pipelines.

See also

Opacity, Transmittance, Scattering, Albedo, Optical density.