In HDRP, the unit of light intensity for a directional light is "lux". According to Wikipedia, lux is defined as "one lumen per square metre". Examples measurements of lux in different circumstances: When creating a new scene in Unity in HDRP, the directional light intensity is set to PI (3.141593), which according to this table equals something like civil twilight. The sample scene in HDRP has a directional light with an intensity of 10, which is something between civil twilight and "public areas with dark surroundings". The FPS sample project has a directional light source of 1,000 lux, which equals an overcast day/TV studio lighting. The entire scene is actually completely white unless a strong auto exposure is used. None of these are even close to the true lux of sunlight. When trying to use a realistic value, the scene becomes so bright that even with maxed out auto exposure settings, it's essentially just white. My questions is this: Why these intensity values? All these values (3.14, 10, 1000) are not physically accurate and seem rather arbitrary. If just taken out of thin air, why 1000 and auto exposure settings for that value rather than 10 and auto exposure settings for it? Is there any guide or best practices regarding lighting in HDRP? It all seems so confusing and arbitrary from the examples I've seen.