# e-ILV

The e-ILV provides free access to all the terms and definitions contained in the international standard CIE S 017:2020 ILV: International Lighting Vocabulary, 2nd edition.

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# 17-21-069

Ep,c; Ec

mean value of photon irradiance on the outer curved surface of a very small (real or imaginary) cylinder that is oriented vertically at a point in space

Note 1 to entry: Photon cylindrical irradiance is sometimes also defined as arithmetic mean of the vertical photon irradiance, Ep,v, at a point

where Ep,v is the vertical photon irradiance for an area element with its normal in the direction φ, and φ is the angle in the plane perpendicular to the axis of the cylinder.

Note 2 to entry: The corresponding radiometric quantity is "cylindrical irradiance". The corresponding photometric quantity is "cylindrical illuminance".

Note 3 to entry: The photon cylindrical irradiance is expressed in second to the power minus one per square metre (s−1·m−2).

Note 4 to entry: This entry was numbered 17-921 in CIE S 017:2011.

Publication date: 2020-12