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Re: Light intensities and matching Cycles
Posted: Fri Mar 06, 2020 11:06 am
by Dade
But are you setting "exposure" parameter to 0 (i.e. EV = 0) ?
It is a bit strange because it is not a valid value and if you check the code you linked before, you will see it will scale everything by 0.0 at the end so you should get a black rendering.
What are exactly your settings ? Sensitivity, exposure, fstop ?
Re: Light intensities and matching Cycles
Posted: Fri Mar 06, 2020 12:16 pm
by polyrhythm
If it helps, 2.5 lux results in "proper" exposure for EV0. Meaning, I guess, middle gray is middle gray?
Illuminance is measured using a flat sensor; if the common value of C = 250 (unit: lux s ISO=lm s/m2 ISO) is used, an EV of zero (e.g., an aperture of f/1 and a shutter time of 1 sec) for ISO = 100 corresponds to an illuminance of 2.5 lux (0.23 fc). At EV = 15 (the "sunny sixteen" amount of light) the illuminance is 82,000 lux (7600 fc). For general photography, incident-light measurements are usually taken with a hemispherical sensor; the readings cannot be meaningfully related to illuminance.
Re: Light intensities and matching Cycles
Posted: Fri Mar 06, 2020 4:18 pm
by chafouin
Dade wrote: ↑Fri Mar 06, 2020 11:06 am
What are exactly your settings ? Sensitivity, exposure, fstop ?
F/1.0, Shutter speed 1s, ISO 100 which corresponds to EV100 0.
polyrhythm wrote: ↑Fri Mar 06, 2020 12:16 pm
If it helps, 2.5 lux results in "proper" exposure for EV0. Meaning, I guess, middle gray is middle gray?
Maybe this is the confusion here? When we say EV 0 corresponds to an illuminance of 2.5 lux, I don't think it means that 2.5 lux should read as a RGB 255 white pixel, but as 0.18 mid gray?
Re: Light intensities and matching Cycles
Posted: Tue Mar 10, 2020 3:32 am
by polyrhythm
Maybe this is the confusion here? When we say EV 0 corresponds to an illuminance of 2.5 lux, I don't think it means that 2.5 lux should read as a RGB 255 white pixel, but as 0.18 mid gray?
Yep, that seems right to me.