Photo from the Nov. 5, 2011, Portrait Photography field trip at the UT Arboretum in Oak Ridge, TN.

The amount of light from the off camera flash was increased from the previous photo. Notice that the background is darker since the flash is brighter than the background. Most viewers would recognize that flash was used in this photo.

This series of photos show the effect of using fill flash on your subject and how it can change the background exposure.