What is luminance?
Luminance describes the visually perceived brightness of a light source in relation to the emitting area and direction.
A small, very bright point light source will therefore have a very high luminance, even though the total radiated power need not be very high. Conversely, an extended light source may radiate a large amount of power even if the luminance is low. An example of this would be a fluorescent tube.
If a light source radiates preferentially in a certain direction, it will appear particularly bright when viewed from that direction. The luminance takes this into account by also considering the solid angle in which the light source radiates. Accordingly, the unit of luminance is lumens per area and solid angle, lm/(m²*sr).
Luminance refers to the perception with the eye. The generalization to any radiation, i.e. also invisible radiation, is the radiance with the unit W/(m²*sr). The luminance can be determined by applying the spectral luminous sensitivity curve of the eye (V-lambda curve).
What is meant by luminance?
Luminance describes the visually perceived brightness of a light source in relation to the emitting area and direction.
In which unit is the luminance specified?
The unit of luminance is lumens per area and solid angle, lm/(m²*sr).
How can we determine the radiance from the luminance?
The luminance can be determined by applying the spectral luminous sensitivity curve of the eye (V-lambda curve).