I did this to show the effects of artificial light and to toy around with the settings.
With Radiance settings low, you can see that the light from the lamp doesn't get very far.
With Radiance Settings high and Soft shadows set to high also, you can see significant improvement.
Same settings as the previous one, but this has the Photons set to Very Many.
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"The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it."
-Terry Pratchett