One question: about the parameter's value of intensity of cesiumSunSky's directionalLight?

one question: about the parameter’s value of intensity of cesiumSunSky’s directionalLight, how to set it’s value in a property limitation if it is not effect some object with material’s effection,for example: refraction or opacity or emissive?
the light is wanted when i open auto exposure, however the function——time of day is not narmal,in other word, is invalid.
in addition, i wonder know cesium using sun sky and ultra dynamic sky in a level, or using ultra dynamic sky in a cesium’s level, it’s practicable?
Talk about sky, true sky, in a unreal world, which selection is the more better choice?