Your job will be to compose and focus. In fact I'd suggest trying to NOT concentrate on the technical aspects of the lighting your first time out. I'm planning on handing out lighting diagrams for all the sets to the attendees. You should be able to see from those how the lights were set and I'll explain the metering and camera settings as well.
To get the most out of working with the models, I suggest that you open your eyes and look with the right side of your brain. What I mean... Is the image you see in the viewfinder pleasing to your eye? In fact, before you even bring the camera up to your eye, look at the scene you're about to shoot. Is the color pleasing? Does the model's body position look pleasing to you? Are there any elements out of place?
The lighting will be set for you by Greg and I. We will have worked out the details of ratios and positions. Your job is to see the light and shadows. Has the model moved closer to or further from you? Is she in the light? Was she standing and now is kneeling? Those relative positions will make the biggest difference in the exposure.
Most of all, just have fun. Fill the viewfinder with the scene you want to capture, focus on the eyes (I'll talk about how to do that), and push the button. Think like a pro, shoot like one (well, maybe that's a little exaggeration

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