Many concerts these days - mainly rock/pop shows - rely heavily on strobe lights as part of the experience. Photographing these shows is challenging, even though there's (at times) plenty of light.
This post assumes knowledge of the basics of electronic flash and flash sync. See this great video for an excellent explanation of these concepts.
During a show, I'm typically shooting at ISO 1600-3200, f/2.8, and anywhere from 1/80 to 1/1000 second, depending on the light. I shoot in manual exposure mode; concerts tend to have extreme highlights and shadows which require careful exposure, and the lighting is usually rapidly changing. (Aside: the Nikon D700 is amazing at low-light photography.)
Strobe lights wreak havoc on that method, especially if they're the primary lighting at the show. I'll focus on that situation here (the same principles apply even if the strobes aren't the primary light source). With that shooting style, most of your photos will be dark because the exposure simply didn't catch a strobe. If a photo did catch a strobe flash, it's overexposed, and chances are there's a dark band at the top or bottom of the photo (as if you tried to use a flash with a shutter speed faster than your camera's sync speed).
The key to fixing this: you can think of the strobe light just like an electronic flash you'd attach to your camera - because they're basically exactly the same kind of light source. When you mix strobe lights with the concert shooting style I described above, there are two issues:
- You're not exposing properly for a flash/strobe
- You're not syncing your camera with the flash/strobe properly
You can fix the first problem by exposing as if you were shooting a flash photo. Flash exposure is determined by exactly two factors: aperture and ISO. (You can think of the flash as being infinitely fast, so the shutter speed has no impact.) Instead of ISO 1600 and f/2.8, you might use ISO 200 and f/11 (strobes are bright). Strobe lights vary concert-to-concert, so obviously this is just an example. Some trial-and-error will be required.
The second problem - flash sync - is a little harder to solve, since you're not triggering the strobes yourself as you would in a studio. (Review the flash sync video I linked above if you don't remember exactly why SLRs have maximum sync speeds.) You have to use a long exposure, for two reasons:
- To increase your chance of catching a strobe flash. At 1/500 second, your shutter is open for 2 milliseconds. Each strobe flash lasts about 1 ms. Even if you're shooting at 8 fps, your chances of catching a strobe at 1/500 s are virtually zero. At 1/50 s, your shutter is open for 20 ms, giving you a much better chance of catching a flash.
- To increase the chance that, when you do catch a strobe, it occurs when neither shutter curtain is traveling in front of the sensor. If you're shooting at 1/200 s, the shutter curtains are traveling across the sensor for most of the exposure, so if you catch a flash you'll probably end up with a dark band on the top or bottom of the photo. At 1/50 second, the curtains are only traveling for a small fraction of the exposure, so you're more likely to get good results.
That explanation may be difficult to understand, so I put together some pictures to help. Suppose there's a strobe flashing 5 times per second:
Now suppose you're using short exposures. Your chance of catching a flash is very small, and even if you do, you'll probably have a dark band somewhere because there's almost no time during which the sensor is entirely exposed:
Finally, suppose you're using long exposures. You have a better chance of catching a flash, and when you do catch one, the shutter curtains probably aren't traveling in front of the sensor:
Keep in mind that your shutter speed is also affected by the ambient light - if there are light sources other than the strobes, you want them to contribute to the exposure. Luckily, with the aperture and ISO settings you're using for the strobe, you'll need a long exposure to catch much ambient light. That works nicely in this case, since catching strobes also requires long-ish exposures.
Note that even with the long-exposure method, you should shoot as many frames/second as your camera lets you, because your chances of catching a flash in any individual photo are still suboptimal.
I put together a video with every frame I shot during an Ella Riot show (back when they were called My Dear Disco). Watch it on Vimeo. You can see that even though I was shooting 8 fps for basically the entire show and using the long-exposure technique, I still got plenty of dark frames and photos with dark bands.
Good luck with this. I'd love to see any photos you shoot using this technique; let me know about them on Twitter (@cdzombak).