Exposing for lightning flash

[Matt Whitney]

Hey, everybody!

I'm gonna be renting one of these Luminys lights to simulate a lightning flash in a rainstorm and I've got a couple questions.

First, how would I expose for this? I'm using the lightning flash to illuminate a character. I'll be shooting on 16mm film. We'll be working with supplemented moonlight, but it's the middle of a thunderstorm, so it will be relatively dark in the shot before the lightning. I'm only going to have the light for the day, maybe the day before, so metering in advance doesn't give me a lot of time to problem solve.

Second, I've never worked with one of these lights before and I was hoping to get input from someone who's used them. I need to light up a character, outside at night with heavy simulated rain. The character is 100ish feet from camera on a 50mm, possibly 35mm. Would the 40K parabolic do the trick for that? The 200K seems like overkill.

Thanks in advance for the answers to my questions.

[David Mullen ASC]

You just have decide how many stops to underexpose for the moonlight and how many stops to overexpose for the lightning. It’s a creative decision based on how well do you want to see things before and during the flash. You’re shooting film so you have a lot of headroom to overexpose the flash while still holding detail. You could, for example, have the moonlight be 2-stops underexposed and the lightning flash be 3-stops overexposed, which would be pretty dramatic. But the lightning could also be less hot - in reality how bright it is depends on how far away and how intense the flash is. You could have a few dimmer flashes that are only at key level and then a big one. If you need to see more action in the room before the flashes, you might decide that the moonlight is only 1.5-stops under (and that also depends on if the moonlight is a side light, frontal, or a backlight.)