Equation for film exposure - need help!
Posted: Wed Mar 30, 2011 11:03 pm
Hello,
I'd like to know how to calculate pixel-values of maxwell-rendering (32bit floating point value in EXR or TIF) into absolute units of cd/m2. So one idea is using exposure value form the camera. But you have to know a conversion factor K like in this equation given by G. Wrad for Radiance:
EXPOSURE = K * T * S / f^2
where:
T = exposure time (in seconds)
S = film speed (ISO)
f = f-stop
K = 2.81 (conversion factor 179*PI/200)
But the formula for film exposure in maxwell is nowhere documented. Can anyone help me figure it out? NL-Team?
thank you and best regards!
I'd like to know how to calculate pixel-values of maxwell-rendering (32bit floating point value in EXR or TIF) into absolute units of cd/m2. So one idea is using exposure value form the camera. But you have to know a conversion factor K like in this equation given by G. Wrad for Radiance:
EXPOSURE = K * T * S / f^2
where:
T = exposure time (in seconds)
S = film speed (ISO)
f = f-stop
K = 2.81 (conversion factor 179*PI/200)
But the formula for film exposure in maxwell is nowhere documented. Can anyone help me figure it out? NL-Team?
thank you and best regards!