Light intensities and matching Cycles

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Dade
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Re: Light intensities and matching Cycles

Post by Dade » Fri Mar 06, 2020 11:06 am

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 ?
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polyrhythm
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Joined: Wed Feb 26, 2020 1:35 am

Re: Light intensities and matching Cycles

Post by polyrhythm » 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?
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.

chafouin
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Location: Tokyo

Re: Light intensities and matching Cycles

Post by chafouin » Fri Mar 06, 2020 4:18 pm

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?

polyrhythm
Posts: 13
Joined: Wed Feb 26, 2020 1:35 am

Re: Light intensities and matching Cycles

Post by polyrhythm » Tue Mar 10, 2020 3:32 am

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.

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