One of the things that I always encourage photographers to do is to experiment with new techniques and practice the things that they’ve learned. You’ll see experiments and exercises scattered throughout this blog, and there’s a very good reason for that– doing something and seeing the results will always give you a better understanding of something than just reading about it. When you practice, the techniques sink into your brain and they’ll be available in the future if you ever need them.
The Roman philosopher Seneca once said, “Luck is what happens when preparation meets opportunity.” As far as I’m concerned, Seneca speaks the truth. You never know when some interesting and unusual photographic opportunity will fall into your lap, and if you know what to do you’re more likely to get the shot.
This evening I was at a shoot that I do regularly– it’s dress rehearsal for a friend’s stage show. I’ve done this shoot every couple of months for the past few years, and I set up the lighting for it myself, so the technicals of the shoot are easy for me. I know from past experience what works best, so before the action starts I drop the cameras into manual mode (no surprise there), pick an ISO, aperture, and shutter speed that I know works for the situation, and I’m then free to think about more important things.
Tonight, however, the friend threw a spanner into the works. “During the first set, we’re going to want to kill all of the lights for a couple of minutes and just use the glowsticks that we’ll have on the stage.” I had a brief moment of thinking that he’d lost his mind, but then I thought about it for a moment and realized that it was no problem.
You see, I’ve already done a lot of very similar work, like this image. This was done with LED glow poi, but I estimated that they would have a very similar characteristics, but that the poi were probably a little bit brighter. I knew from experience that I could get good but slightly-underexposed results with glow poi at f/4 and ISO 400, and whatever shutter speed was right to get the amount of motion I wanted. (One of the interesting things about shooting moving lights is that longer shutter speeds don’t make the image brighter, but instead give you a longer motion trail. Do you see why that is?)
I was shooting most of the show at f/4, ISO 1600, and 1/60 sec. I estimated that f/4 and ISO 1600 was probably about right for the glowstick shots, and that I’d probably want exposures of about one second. I also knew that autofocus wouldn’t work very well, and that I should pre-focus and keep the lens in manual focus mode.l
We discussed what the cues would be for cutting the lights, so I knew when it would be happen. When I saw the first cue I changed the shutter speed to one second, switched to manual focus, and waited. We cut the lights, I got a few shots of pretty moving lights, and then we brought the lights back up and continued with the set. When the lights were back on I changed the camera back to 1/60 and autofocus.
I got one good shot from that segment, which is about what I would have expected. The exposure I picked was just about spot on, and because I was shooting in raw mode I had the latitude I needed to make final adjustments on the computer.
If I’d never practiced this sort of shot I would have had no idea what to do with the unfamiliar situation. However, tonight practice and experimentation sereved me well– when an unusual opportunity arose, I could make my own luck and get the shot.
Now it’s your turn– go find an unfamiliar situation and play with it, so that the next time you run into something similar you know what to do. What are you waiting for?
Stop Shooting Auto! 
You said, “(One of the interesting things about shooting moving lights is that longer shutter speeds don’t make the image brighter, but instead give you a longer motion trail. Do you see why that is?).” I hadn’t thought about that until now and I’m curious as to why that is. But I can’t even dream up a hypothesis that would answer the question.
OK, how to explain this.
Imagine that you have a perfectly dark room, and you just open the shutter and keep it open.
Now imagine that you have a tiny light, maybe a single LED. If you just pulse the LED very quickly, then close the camera’s shutter, you’ll get a single photo that has a (probably faint) point of light.
If you do the same thing, but instead of pulsing the LED you keep it on for 10 seconds, you’ll get a photo with a super-bright point of light. It would probably “burn in” at that point and just massively overexpose.
It’s exactly the same thing as if you took a picture at 1/10 sec as opposed to 10 seconds– the camera will see the light for a very short period of time or a very long period of time, and will therefore capture a small amount of light or a lot of light, depending. You are effectively determining the shutter speed by the amount of time the light is on (because it’s perfectly black when it’s not) rather than how long the shutter is open.
Now, imagine you do the same exercise but you turn the light on and then walk across the room with it pointed at the camera. What you get is effectively the same as if you turned the light on for 1/10 second, moved a millimeter, turned it on for 1/10 second, moved a millimeter, etc. The light isn’t on for very long in one place, so it doesn’t “burn in”. Rather, you get a trail of lights that are all relatively dim.
If you moved the light back and forth over the exact same area, you’d get something brighter. In the bottom photo you can see that the area where she was swinging the glowsticks in a circle is much brighter than the streak across the bottom. That’s because they spent more time in the same place, and I captured several rotations.
I get it. It’s like painting with a can of spray paint. Sortof.
Why, if she was swinging lights, are her arms not blurred? And what made the segments in the funnel-shaped lights? This is a cool photo because of what it does with the light. It’s also interesting to try and figure out what that looked like in real time with a pair of eyes. :)
@TJ: I’m going to assume she was using her wrists and fingers, not her arms, to move the glowsticks.