Revit to UE4 lighting discrepancy (scene looks like midnight during daylight)

[KM3d300]

Hi,

Long time offline render user here (vray way back when), however decided to jump on the ue4 train with a few projects.

When using Datasmith to bring my scene into UE4 from Revit, I'm pretty happy with initial results.

However the main issue seems to be that lighting levels

Artificial/interior lights seem to be a factor of 10x the amount of the skylight + sun. So when one stands outside the building, the interior glows brighter than daylight making it look like midnight.
I've checked an all interior lights are setup to be roughly around 80cd.

However the sun, by default in ue4, is 3 cd??? Isn't the sun like around 1,600,000,000 cd?

Is this something that needs to be correct first in Revit or should I be doing something in UE4 to make the sky physically correct? Thanks.

[KM3d300]

After some investigation it seems point lights, areaa lights can be set in lumens but skylight only has an arbitrary setting?
As a newcomer to UE4, are lights set by 'eye" and not the V-Ray/Corona/Mental Ray/Arnold way of using a photometric scale?