Area lights have many additional options. Most importantly, any geometry
can be selected to act as "geo light"
Light Spread
Normalize Intensity by Area
Visible to Primary Rays
Makes area light visible to primary (a.k.a camera) rays.
Two Sided
When enabled, area light will illuminate from both sides. Note that this has no effect with the sphere shape.
Default Shape
Allows you to select the a different number of shapes (left to right): square, sphere, disk and sylinder.
Select Geometry ...