How to Make Magic with a Flash and Rear Sync with Levi Sim

How to Make Magic with a Flash and Rear Sync with Levi Sim

January 27, 2015

...words and images by Vanguard Professional Levi Sim

The most powerful flash setting you have is the one that controls when your flash fires. This setting works for your pop-up flash, for a speed light on your camera, and for any off-camera light, you’re controlling. It’s called Rear Sync, or 2nd Curtain.

What you need:

  1. Camera–point and shoots may not be capable and your iPhone can’t do it, but many bridge cameras and every changeable lens camera I’ve ever handled will work
  2. Flash (pop-up, Speed light, mono-block, power-pack, and head, nuclear bomb–anything will do)
  3. Tripod–strongly recommended for the best results and replicability

Why’s it Called Rear/2nd Curtain?

The shutter in your camera isn’t like a door that swings open and closed. It’s more like two sliding doors–the first one slides open and the second slides closed after it. This is why sync speeds are important when working with flash–if your shutter speed is too fast, the doors will be partly closed when the flash goes off.

The default setting for your flash is to fire as soon as the doors are open(front sync/1st curtain), and then the second door closes having let the flash illuminate your subject. When you have the slow shutter speed and a subject that’s moving, however, you’ll see that the flashlights your subject, but then as she keeps moving she blurs through herself, possibly becoming unrecognizable (and possibly looking very cool). This is when the flash fires at the beginning of the exposure.

Set it to rear sync (Nikon) or 2nd curtain (Canon, Panasonic) and the camera fires the flash at the end of the exposure, just before the second door closes. This way, your subject is moving and blurring, and then gets frozen by the flash at the end. This usually makes the face sharp and recognizable, and yields more repeatable results than a front curtain.

I set my cameras to 2nd curtain and leave them there. You’ll really only notice the difference when speeds are slow and there’s some movement on either side of the camera. Purposely using a slow shutter speed is called “dragging the shutter”.

(Note: if you set to 2nd Curtain and use anything but Manual mode with your pop-up flash, you may notice that the camera chooses a longer shutter speed than it does in 1st curtain mode; this is because it’s allowing the ambient light to burn in and balance with the flash, which is generally a nice thing…unless you’re trying to handhold a 1/4 second exposure on the wedding dance floor and aren’t expecting it. Practice these settings before you’re in a situation where it counts.)

Move the Camera and Drag the Shutter

Dragging the shutter is commonly used to allow ambient light to burn brighter in a picture–usually so it’ll match the brightness of strobe light (FYI: strobe=flash=strobe). But if you want to really have some fun, set your shutter speed slow, adjust the flash and other settings so the picture looks good, then move the camera during the picture.

For this portrait, I set up the picture based on a quarter of a second exposure. We’re downtown after dark, so there are lights in the background. With the camera mounted on a tripod, I locked focus on her face, then panned the camera to the right so she was out of the frame, then fired the shutter and quickly panned the camera back the other way so she came back into the picture. The flash fired at the end of the picture, freezing her face in place with the blur trailing into her.

I really thinks it’s important to use a tripod for this. It’ll take several tries to get the timing right, and then once you’ve got the timing down you can start to alter other variables, like facial expressions. If you’re hand holding, though, you’ll end up missing the best expressions. If you don’t have a tripod, then by all means, give it a go hand held, but I think you’ll see better results on some sticks. Here are a few of the tries I made at the same time as the shot above.

Move the Subject and Drag the Shutter

Another great way to use rear sync flash is to move the subject while the camera holds still. Using the tripod here makes sure you can repeat the picture, but it also allows you talk to your subject and give coaching and suggestions without having your face mashed up to the back of a black box.

For these portraits, I was shooting in the daytime at the beach with dense cloud cover which made the sky dark enough that I didn’t have to stop my lens too far down. Using f/4 gave me a shutter speed of just 1/40th of a second, which is slow enough if my subject moves enough. More importantly, f/4 is a big enough aperture that I don’t have to turn the flash all the way to full power to get enough light. A slow shutter is my goal, but when it’s bright outside I have to get that speed with a smaller aperture, and aperture is the primary limiter of flash brightness. I’m afraid this isn’t a flash basics article, so let’s move on.

I wanted my subject to appear solid near the light (on camera-left) and have a trail from the right. I asked her to lean toward the light, got the exposure just right, locked focus, then asked her to lean away from the light and quickly lean back toward it.

I like this technique because it really stands out. There’s sometimes a natural drop shadow around her where her body was for a portion of the exposure, but it moved before the flash fired. Other things about this picture: I used an orange CTO gel on the flash, which makes whatever it lights orange, and set the camera to tungsten white balance, which makes the whole picture blue; the two colors cancel where they overlap. Dusk is a great time to use this technique, and this article details that process. This was a really fun day at the beach–especially because I got to shoot with my friend Megan, and fellow author, Lisa Robinson.

Remember, it usually takes several tries to get the subject moving the right way and expressing the right way–you gotta get a tripod for a this stuff.


Now Mix the Light and Shoot on Black

The previous examples were made outdoors with speed lights, and I had no control over the ambient light conditions and backgrounds. One thing you’ll learn as you start doing this is that the background makes all the difference. street lamps in the back can end up showing through your subject’s face, and a sky that is too bright won’t give enough definition. Black backgrounds give the best results for showing off your subject because they don’t expose through the subject. Look at these on white and you’ll see what I mean.

Compare the images above with this one. There is little change in exposure settings, only in switching the background to black, which gives a more solid portrait at the end of the exposure.

The light you can see on the left side of the frame is just the modeling lamp from one of my strobes; it’s a 60 watt light bulb, and it’s tungsten. At the end of the exposure, the flash on the right side of the frame fired, and it’s a big 4′ square softbox. Now I’ve got control of both my ambient light (the light bulb) and my flash. As my subject dances across the frame the light bulb burns her blurry movements onto the sensor, then the flash freezes her pose at the end. Longer shutter speeds give her more time to dance, but they also brighten everything in the room, so it takes some experimenting to get things looking how you like. I love the silky look of her body blur as it moves across the frame.

Let me beat the dead horse: use a tripod! There’s one important technique for making this all work: excitement. I tell the subject what to do, we make a frame or two, then I show her the results so she knows what we’re going for. When she sees this incredible effect right on the camera, she always gets excited, which makes her more patient to practice a few more times to perfect the image. The tripod makes this repeatability possible, and it’s more respectful of her efforts because it guarantees good results.



If you can set your camera to rear sync or 2nd curtain flash, you can make this kind of picture. Try it with your pop-up, but I bet you’ll be wanting something off camera in no time. A tripod will make the pictures better, and shooting on a black background makes faces more distinct. Give it a shot and knock your subjects’ socks off with an incredible image right in the camera that doesn’t require any photoshop magic.


Levi Sim

This article originally appeared on PhotoFocus. See it here. Follow Levi on Twitter, Facebook, his website, or on Google+