Area of the surface
The area on the surface that the spatial angler cuts into a sphere.
The area of the sphere
Refers to the area of the sphere.
The distance from the light source to the illuminated surface.
The area on the flat surface that is illuminated.
Refers to the light that hits the current surface.
The total luminous flux that radiates from the current light source.
Refers to concentration of light in one direction.
The one which spreads the light measured in steridians.