Radiance
1-1-135
Radiance (in a given direction, at a point on the surface of a source or a receptor, or at a point on the path of a beam)
Quotient of the radiant flux (d2Fe) leaving, arriving at, or passing through an element of surface at this point and propagated in directions defined by an elementary cone containing the given direction, by the product of the solid angle (dO) of the cone and the area of the orthogonal projection of the element of surface on a plane perpendicular to the given direction (dA/cos ?).
Symbol Le
Unit watt per steradian per square metre (W/sr/m2)
Reference: C.I.E. (modified)
Note: 1 Since the quotient of dFe and dO is the radiant intensity dIe, the radiance is given y
Note: 2 If the radiant intensity Ie produced by a plane radiant surface of finite area A in a particular direction (making an angle ? with the normal to the surface) may be considered uniform over all points of the surface and of value Ie?, then the radiance Le? of the surface in the particular direction is given by
Note: 3 For further definitions see C.I.E.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
