Step-by-step guide to cross-lighting

Apparently this photo was in the Press & Journal last week although I never saw it myself. But I do know that it was used over on Strobist today as an example of cross-lighting which is a huge compliment.

I've been meaning to do a write-up about the procedure behind cross-lighting, so for the benefit of people clicking through from Strobist I'll do that now.

Ambient exposure:

The first thing to keep in mind is that you're exposing your ambient for the sky. Forget about the ground. When you try this for the first time and you chimp the test shots on your camera you'll probably be worried that the finished photo is going to look awful. But it won't. This is the correct way to do it.

So with your camera in manual mode and metering for the whole frame, point it at the sky in the direction that you'll be taking the photo. Choose your shooting direction based on the position of the sun, which should ideally be at 45 degrees behind the subject. For this shot the sun was behind the subjects to frame right.

Set your ISO to its lowest setting and your shutter speed to the fastest speed that your camera can flash-sync at, probably 1/250s. This allows you to tame the ambient while still giving your flash a fighting chance of matching sunlight. Then adjust the aperture to correctly expose the sky.

Now when you take a test shot you'll find that the sky looks a little darker than it usually does in photos, and the ground looks under-exposed. Perfect! This is what you want. This is the beginning of that natural-but-surreal look that is so evident in cross-lit photos.

Flash exposure: 

Now it's time to set-up your flash, which should be directly across from the sun on the opposite side of the subject.

You'll probably need to use bare flash because you need a lot of power and diffusers eat too much. If you're shooting on an overcast day, or when the conditions just aren't very bright, you might be able to set your flash to 1/4 or 1/2 power.

But it was ridiculously bright sunlight for this photo so with my shutter speed at 1/500s and the sky metered at f/8 the flash was set to full power straight away, and I wasn't sure even that would be enough.

Time for a test shot to check the flash exposure so I held my hand over the middle of the boat, where the subjects would be standing:

I wanted to use a rear light to enhance the effect of the sun so I positioned that on the other side of the boat. This was at half power because it was a lot closer to where the subjects would be standing. Here's the customary hand shot to check its effect:

I'll admit that I don't know what effect, if any, this flash had in the final photo. During the 23 shots that I did of the musicians I can be sure that there will have been times when it hadn't recycled fast enough and so didn't fire, but I can't tell which shots it fired for and which it didn't. So in conclusion I would say that you probably don't need a trim light for cross-lit shots.

With the ambient exposure set and the flashes set it was now just a matter of waiting for the musicians. Once they arrived I explained what I was trying to do and roughly how I wanted them to position themselves in the boat. Then I let them get on with it while I grabbed some more test shots, firstly checking that the ambient exposure hadn't changed significantly:

By this point of setting up a cross-lit shot you might be better relying on your histogram rather than the preview image. You'll have a lot of dark tones in the image with some spiking in the highlights for the brighter areas of sky. This is the histogram for that test shot:

Make sure it all works: 

Time now for a final check of your flash exposure, and the easiest way to do this is to just walk into the frame and take close-ups so you can see people's faces more clearly on your preview image. If their faces are too dark or too bright then change the power of your flash or move it closer or further away. What you DON'T want to see when you're already at full power is that your flash isn't providing enough light, and that's exactly what happened on this occasion:

That looked about one stop under-exposed to me, so my only option was to open my aperture from f/8 to f/5.6. That was going to make the ambient brighter than I wanted it to be but there are times when you have to choose between doing the shot less-than-perfectly or not doing it at all, and the clock was ticking. So I opened up to f/5.6 and did some more test shots to make sure the flash exposure on people's faces was correct, which it was:

Make sure you do test shots that cover the full width and height of the area that you need the flash to light. For example it would be no good doing a test shot of someone in the middle of this set-up and then finding that the people on the edges weren't properly lit.

Next a quick dash around to behind them to check what the combination of sunlight and rear flash was doing. Looked okay, a couple of stops over-exposed which is what you want, no time to change it anyway:

Doing the shot: 

With the settings locked I made a few adjustments to how the group was set-up, went to where I'd be taking the shot from, and asked them all to make sure they could clearly see the main flash without anyone else's head blocking their view. That's one way to check (approximately) that you won't get anyone's face in shadow: If they can see the flash then the flash can see them.

(I did actually know that we were okay for this shot because I'd checked already, but I might start using this method in future so this was an experiment to find out if people will understand what I'm asking them to do.)

We then did 23 shots in about two minutes, with the 22nd frame being the best of the bunch, despite the flaw of the guy standing at the back, third from the left, having his face slightly obscured by the guy sitting in front of him. Kind of ruins the shot for me but there you go. My fault, not theirs.

It's always a good idea to grab some extra shots if you've got time, so I quickly took some from low down and some from high up, holding the camera above my head and getting the girl in the middle of the group to tell me if it needed to be raised or lowered to point straight at her. For these shots I just told everyone to make themselves the most dominant person in the frame. Didn't get anything particularly good but it's worth trying.

Here's an outtake from the overhead shots that shows where the rear flash was positioned in relation to the group:

And that's how you cross-light a shot using one flash and the sun. You can pretty much disregard the rear flash as its effect was negligible at best and the shot would have worked just as well without it.