<Dl> <Dd> L v = d 2 Φ v d Σ d Ω Σ cos ⁡ θ Σ (\ displaystyle L_ (\ mathrm (v)) = (\ frac (\ mathrm (d) ^ (2) \ Phi _ (\ mathrm (v))) (\ mathrm (d) \ Sigma \, \ mathrm (d) \ Omega _ (\ Sigma) \ cos \ theta _ (\ Sigma)))) </Dd> </Dl> <Dd> L v = d 2 Φ v d Σ d Ω Σ cos ⁡ θ Σ (\ displaystyle L_ (\ mathrm (v)) = (\ frac (\ mathrm (d) ^ (2) \ Phi _ (\ mathrm (v))) (\ mathrm (d) \ Sigma \, \ mathrm (d) \ Omega _ (\ Sigma) \ cos \ theta _ (\ Sigma)))) </Dd> <Ul> <Li> L is the luminance (cd / m), </Li> <Li> d Φ is the luminous flux (lm) leaving the area d Σ in any direction contained inside the solid angle d Ω, </Li> <Li> d Σ is an infinitesimal area (m) of the source containing the specified point, </Li> <Li> d Ω is an infinitesimal solid angle (sr) containing the specified direction, </Li> <Li> θ is the angle between the normal n to the surface d Σ and the specified direction . </Li> </Ul> <Li> L is the luminance (cd / m), </Li>

State any four places in which luminance level required