Assuming that a lot of folks here use soft boxes as key lights for interviews, what do you do when there isn't a huge amount of space to play around in to prevent spill onto the background (and hence loss of control over the background lighting). It seems insoluble for small sized locations.
Greg

Use an eggcrate. They are not cheap but really cut the spill light you get from a naked softbox.

Use an eggcrate. They are not cheap but really cut the spill light you get from a naked softbox.

Jack, thanks for the answer.

Eggcrates are the best tool. They are rated in beam angles (like 20, 30, 40, 60 degrees). The smaller the angle, the tighter your beam (less spill), but your effective light output goes down as well. Jack's right though, they are pretty pricey, so it's unusual to have a big selection of them. If the space is really small, you may still have problems with spill. Another tool that may be helpful with softboxes is a big flag (like a 4x4). They can be used somewhat like a barn door to cut some of the light off the back wall without cutting it off the talent.

Black Foamcore + Gaffers Tape = Cheap Flag or Barn Door for your softbox