I’ve messed with this but can’t figure out what IBL Compat Specularity does - can anybody fill me in?
In Bryce 6.1/6.3 IBL, specularity was connected to HDRI Effect. With Bryce 7.x, we got a separate specularity control. The option Apply to light source next to Intensity makes it Bryce 61/6.3 compatible because HDRI Effect was coupled to Intensity. This was a bit confusing because you could not adjust the backdrop brightness without adjusting HDRI Effect.
Compat (ible) Specularity does only properly work if the Intensity option Apply to light source is also enabled (it is only then compatible to Bryce 6.1/6.3). Intensity not only controls the backdrop brightness if this option is enabled, it acts also as a multiplier for HDRI Effect and Specularity. I tried to compile those light thingies into a PDF (500 KB).