Stationary SkyLight's metal brighter than Static

I create a material with metal=1, roughness=0, specular=0 for test. SSR is disabled.Only one SphereReflectionCapture in level.

113292-test1.png

113294-test2.png

The first is Stationary SkyLight and the sceond is Static.

I captured a frame.
When SkyLight set as Stationary. Reflection will compute with these two cubemaps:

113297-test3.png

Left is Sphere Reflection Capture captured scene closer than SkyDistanceThreshold. Right is SkyLight’s cubemap which capture everything further than SkyDistanceThreshold.

When SkyLight set as Static. Reflection will only compute from Sphere Reflection Capture’s cubemap, which capture scene with no distance limit:

113298-test4.png

Why picture3’s left brighter than picture4?

If I set SkyDistanceThreshold x100 when SkyLight is Stationay, now Sphere Reflection Capture can capture SkySphere. Picture3’s left will look same as picture4, and final screenshot same too.

Another question is when SkyLight is Static, why not just use SkyLight’s cubemap as default to compute reflection like stationary?
As I know, Sphere Reflection Capture only affact pixels in it’s radius. If I have a very large map and I don’t want place so many captures by hand, there will be only SSR on metal surfaces?

The following picture shows hide Sphere Reflection Capture’s scene: