I've had a few recent photo shoots where there have been breaks in the action between makeup changes. In the past I'd use the time to move lights around, look at the images I just took or chat with others in the studio. However recently there have been multiple models in the shoots. For fun, and for the model's (and my) portfolios I've been setting up a separate backdrop or section in the studio to do a few impromptu shots. Normally, just 9x12's or head shots. It might be as simple as doing a few shots against a grey wall. Or 3-4 shots against a small black, white, or colored piece of foam core mounted on a boom with a clamp. Perfect size for a headshot.
These are generally not part of the studio session and I will send them to the model separately. Lighting tends to be fairly straight forward. Rarely more than 6-10 total shots.
Bottomline, it gives me a chance to take a few shots outside of the main theme and to have something to do between makeup changes.
Here are a couple I took of model Jade Amber this past weekend between sets. The first was Jade just laying down on the seamless we had just shot on, and the second was against a grey wall in the studio. Even though these weren't part of the images we were planning for the client she still rocked it.