These are just two of the many possible light sources.
Never place any light source directly in front of a television.
Here the light source is the sun moving in the sky.
This rule does not work when the light source is near.
The light source used to project the photo is what begins the process.
That is the effect of the different light sources at the store and home.
A dark area has limited light sources, making things hard to see.
The maximum possible value for any light source is 683.
Another has you moving a light source to create a certain shadow on the wall.
Then I turned, slowly, to check for any possible light sources.