Map Editor : How to set up a light from emissive meshes

Select an emissive mesh on the viewport:

Open its properties (double click or press F4), click on Static Mesh Actor > Static Mesh Component > Lightmass > Lightmass Settings and enable “Use Emissive For Static ligthing”:

Click on “Build > Build All” to build the map:

Here is the result. You can see that the light is too strong:

To correct it, in the StaticMeshActor Properties, modify the parameter “Emissive Boost“:

With a value of 0.2, you should have this result (after building the map):