Luminance: why surfaces look differently bright
Illuminance describes arriving light. Luminance describes the light a surface sends in a particular direction.
Luminance is measured in candela per square metre (cd/m²). It helps explain why a white wall, dark floor and polished metal component can look very different under the same illuminance. Materials, reflection and viewing direction therefore belong in a lighting brief alongside luminaire output.
The relationship between neighbouring surfaces also matters. A bright luminaire against a dark background may be uncomfortable; a brighter surrounding area can create a more balanced impression. Adding more lux to the desk does not automatically resolve this contrast.
Assessment should include normal viewing directions, screens and representative material samples. Renderings support discussion but do not replace a professional evaluation. For demanding tasks, luminance measurements can help identify the source of distracting contrasts and compare proposed changes under consistent conditions.
What to clarify for your project
- Specify representative surface finishes.
- Consider bright sources and dark backgrounds together.
- Check contrasts from the actual working position.
Remember: Assess the task, materials and viewing direction as well as the lux value.