Just like your focus, light has depth of field.

For this layer of control, we are going to look at two different pictures. Everything will be the same except for one thing: The distance from our light to our subject will change. Nothing else. In particular, the subject-to-background distance will not change.

Exhibit number one is a dark portrait of Dean, situated a few feet in front of a white wall, pictured above.

White wall? Yes, white. But it doesn't look white, does it?Read more »

http://strobist.blogspot.com/2016/07/lighting-102-distance.html