Autodesk 24000-000000-9860 - Revit Architecture - PC User Manual page 1173

When you render an image, you can use light groups to turn on or off entire sets of lights, rather than
controlling lighting fixtures individually. You can also use light groups to control dimming of lights in a
rendered image.
Task lights are turned on; central light is turned off.
Central light is turned on; task lights are turned off.
Light groups are available in all relevant areas of Revit Architecture. However, settings to dim or turn on or
off light groups (or individual lighting fixtures) apply to individual 3D views only.
NOTE The number of lights in a 3D view to be rendered can significantly increase render time. Use light groups
to turn off unnecessary lights in the view. See Render Performance and Lighting on page 1173.
Light Groups | 1135