Hello Radiance users,
I have a question regarding how Radiance calculates luminance values. I understand that the following equation converts radiance values into luminance using the luminous efficacy factor of 179.
𝐿 = 179 ∗ (0.2651 ∗ 𝑅 + 0.670 ∗ 𝐺 + 0.065 ∗ 𝐵) [Eq. 1]
Are there generally adopted boundaries for RGB? In “Spectral Daylighting Simulations: Computing Circadian Light” (Inanici et al. 2015) the authors write the following:
“The wavelength intervals for a standard three-channel (RGB) imagery in Radiance are calculated as 380-498 (B), 498-586 (G), and 586-780 nm (R) based on their respective coefficients in Equation 1.”
However, in "Creating physically accurate visual stimuli for free: Spectral rendering with Radiance (Ruppertsberg & Bloj, 2008) propose using equidistant bins for RGB.
Since the coefficient of each bin can influence the output, how should the spectrum be divided between these bins? Equidistantly or does Radiance, in fact, define spectral boundaries for RGB?
My second question is regarding “Spectral Daylighting Simulations: Computing Circadian Light” (Inanici et al. 2015). We have recently tried to reproduce the coefficients published in the paper for photopic and circadian response functions (Lucas curve) using trapezoidal rule for integration to find area under the curve of each of the bands. Unfortunately, we could not reach the same values as in the paper with this approach or anything else that we tried. Perhaps someone already tried to replicate this and can explain the missing points.
Any feedback on these points is highly appreciated!