I have a scene (attached) where a perfectly diffuse partial sphere gets illuminated by a plane whose texture is set up as an emission BRDF.
My .blend file: https://www.dropbox.com/s/k7w36wlfoewie7p/scene.blend?dl=0
The light plane is so small relative to the light-object distance, that changing the texture has almost zero effect on the rendered images.
The scene is out of my control, and I'm hoping for physically accurate renderings. Is there anything I can do to make the renders responsive to the change of light patterns, even if the light patterns are really far?