At our recent inaugural Anytime Light Workshop there was a discussion of light spill and light modifiers. The workshop gave us a great opportunity to shoot a single subject in the same setting with different modifiers. Our model Dagny posed while we switch modifiers, but otherwise shot from the same location with the same settings. We only adjustmented the light power to compensate for modifier efficiency.
The light was placed high and to audience left. Dagny was about 5 feet in front of the wall.
As you can see, there is quite a range of effects and moods. Some modifiers, like the long throw produce fairly sharp shadows due their relatively small size. Adding a grid limits spill so the back wall falls off to black. Grids have a similar effect on larger modifiers. They may also change the way the modifier wraps the subject. See the 3×4 softbox with and without grid.
Of course, perceived size (from the subjects point of view) of the modifier also controls “wrap” or how “soft” the light is. The long throw is essentially a point light source producing “hard” light and sharp shadows. At the other extreme are the large PLM (a huge umbrella) and the 3×4 softbox. These modifiers project light at the subject from a very wide angle and thus produce extremely soft, sometimes invisible shadow transitions. They also tend to spill large amounts of light on the background unless carefully positioned or gridded.
Each modifier has it’s own character. As photographers, we get to pick and choose which to use to produce the results we want. Part of the fun of photography is learning about subtleties like this and exploiting them in our work. As always, the best way to learn is to get out and shoot with the various modifiers available to you.

Andrew is a photography instructor teaching students of all skill levels in Austin, TX through Precision Camera and independently in San Diego, CA. He runs workshops around the United States.
He is a self taught experiential learner who is addicted to the possibilities that new (to him) gear open up. He loves to share the things he has worked out. Andrew started with a passion for landscape and night photography and quickly branched out to work in just about every form of photography. He is an ex-software developer with extensive experience in the IT realm.
Andrew is a full time wedding and commercial photographer in both Austin and San Diego. Andrew is a club founder and multi-time past president of North Austin Pfotographic Society.