I started working with real light values a few months ago for cinematic projects for several reasons. correct light blending, takes guessing out of working, realistic camera values, high dynamic range, crisper sunlight that feels hot and getting rid of that unreal look. Lumen however seems to have a problem with high values coming from sunlight - it is set at 200,000 lux. I work with Ultra Dynamic Sky. When changing from day to night the problems start: objects start glowing like they have light burnt in or something. It seems to come mainly but not exclusively from SSS materials. It doesnt even go away over time. It does not matter if camera is auto exposure or manual. its definetly glowing. It is also visible in Lighting only mode.
The only way to get rid of it is to fly around with the editor camera for a bit, then it clears up.
My guess is this is most likely just an issue with the update speed; Lumen doesn’t handle sudden directional light changes well. Given enough time, at default update speed it should eventually manage to update all the probes, but you can speed it up by adjusting the post process setting.
For the rest, is it working fine with extended luminance values? I tried time ago, buy it was weird to work, as actors billboards went super brighty, etc.
PS: I created the same scene with default lighting values and with extended luminance, trying to get the same intensity, and they looked exactly the same, isn’t it?
Yes, they should look about the same when you have auto-exposure turned on (i find the bright spots look a touch hotter…but maybe that was just my exposure setting). For games i have no clue if it would make sense to use this. probably not in most. For cinematics or archviz it is a bit different. There are benefits that come when working with real light values.
1 // Preparation stage: it’s easier to work with real values because you can look up or measure (even with your smartphone) how much a light source is emitting. If you are after realism it takes the guess-work of finding the right light balance out of the equation.
2 // Correct light blending Lets say a headlight of a car…it is bright at night but you barely see a light cone at day because daylight is so much brighter.
3 // Post effects Maybe you notice that the threshold for bloom dont really seem to work in the default brightness. but with the higher values these get nice and easy to adjust.
4 // Camera work If you have a background in photography, maybe you are even working with a camera person you will want to make use of real camera values in a physical camera setting. you can only do this if your lighting is based on real values.
5 // Post Production It adds a lot of range in your high bit depth EXR. It then behaves like real camera footage and the color graders are happy, especially when working with ACES
However when auto exposure is turned on, it crunches all the high and low values down into something digestable and should end up at around the same. FYI I’m only working with Ultra Dynamic Sky, I’m not really sure what the standard UE sky settings are
