Difference Between Luminance, radiance , illuminance and irradiance

 

Difference Between Luminance, radiance , illuminance and irradiance

 
ParameterPHOTOMETRY
Spectral Range 10nm-1µmRadiometry
Spectral Range 380 -780 nm
LuminaceIlluminanceRadianceirradiance
Defthe intensity of light emitted from a surface per unit area in a given direction.It is a measure of photometric flux per unit area, or visible flux density.It is the radiant power from unit area to solid angle.It is a measure radiometric flux or radiant power per unit area
Unitscd/m2Lm/m2 or LuxWm-2Sr-1W/m2
DescriptionIt describes the measurement of the amount of light emitting, passing through or reflected from a particular surface from a solid angle. It also indicates how much luminous power can be perceived by the human eyeIt describes the measurement of the amount of light falling onto (illuminating) and spreading over a given surface area. Illuminance also correlates with how humans perceive the brightness of an illuminated area.radiance is the radiant flux emitted, reflected, transmitted or received by a given surface, per unit solid angle per unit projected areaIrradiance measurements should be made facing the source, if possible.
 Luminance
Dependence on distance Dependence on distance Dependence on distanceRadiance is independent of distance for an extended area source, because the sampled area increases with distance, canceling inverse square losses.The irradiance will vary with respect to the cosine of the angle between the optical axis and the normal to the detector.