I am trying to get my head around physically based lighting in Blender.

I read somewhere the Cycles Sun Lamp is measured in W/m² so assuming that bright sunlight is measured at 120000 lux (https://en.wikipedia.org/wiki/Daylight) my intensitiy for the blender sun will be (given that 1lux = 0.0079 W/m2 for sunlight) around 980 W/m². This matches more or less with the readings from wikipedia, that states that the max sun intensity depending on its distance from the earth is 1050 W/m² (https://en.wikipedia.org/wiki/Sunlight).

Using the filmic Blender add-on I am now way overexposed. Here comes my first question: where do I compensate for that? I found two exposure sliders within Blender. One directly in the color management tab, which I assume doesn't affect the final rendering, but only the viewport lut. Or do I use the exposure slider under the render tab/film?

Second: How does cycles handle the light contribution from environment maps? In what relation do they stand to the sun intensity as they have a seperate intensity slider. Is there a rule of thumb to get them in the right ballpark?

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    $\begingroup$ Please only ask one question per post. You are welcome to ask as many separate questions as you need as separate posts. $\endgroup$ – Ray Mairlot Aug 6 '17 at 13:06
  • $\begingroup$ please split this post in two different questions. $\endgroup$ – user1853 Aug 7 '17 at 1:57

Use the false colour look in combination with a CDL node (What is the the ASC-CDL node?) to bring your values within the range of the color transform.

See also this related post: How to scale properly HDRI image, to be used in ASC-CDL HDR render?

and this one (somehow outadted, but should give you an idea): Using the False Color look in combination with the CDL Node to work on Wide Dynamic Range scenes

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