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Unreal exposure to real life light values

Hi all

I’m looking for light value parameters / histogram for exposing a scene in unreal 4 used in conjunction for real time green screen compositing.

For example how do i mimic the same lux values in unreal engine 4 for a light like a 650w lamp (as an example light) so that the lighting matches a real light through a camera with X amount of dynamic range. (Which in our case will be a black magic Ursa G2 that has 15 stops of dynamic range.)

I’m aware that there is a manual exposure setting in the post process volume, which you can set how the scene is exposed via the inbuilt post process exposure tab under “camera”, but i’m failing to get my head around it how it works and theres little to no information on the subject (probably because people rely on the inbuilt auto exposure histogram.)
Regarding IES files, which i have access to of my ARRI 650w lamp, which contain the same shape / size, but is measured by a “intensity” parameter, which doesn’t tell you the differences / compensation of the light value. Does IES Intensity scale set at 1.0 mean that the light replicates the default real life value of the light? and what light value is it measured in? and if so, how do you match unreal engines dynamic range to that of a Ursa g2 if thats the way to do it?

Thanks

That is a good question, I always assumed that an IES when unchanged carries the original data and luminance strenght. I’m not pro at that stuff but I think that that is how it works.

Check this out for lights https://learn.unrealengine.com/course/3339364