“Did you know that there are curtains in your camera that can affect your flash photography?” Photographer David Bergman in another awesome episode from Adorama TV explains:
In most modern DSLR cameras, there are two shutter curtains that move separately, to expose the digital sensor to light coming through your lens. You normally don’t have to think about it but when you use a flash, you can set it to fire at the beginning of the exposure right after the first curtain opens up, or at the end of the exposure, before the second curtain covers up the sensor.
With a fast shutter speed, you really won’t notice a difference because the shutter isn’t open for very long, but things get more interesting when you use a longer exposure time to demonstrate.
In this video we are shooting a picture of a dancer leaping through the air. Using LED strip lights on her, we can really see the movement better.
Here is the photo taken when using a long one second exposure, and no flash. You can see she’s just a big blur.
Now let’s add in some flash to freeze the dancer at some point during her leap.
The default is first curtain sync, so the flash fires at the beginning, and then the rest of the time she’s in the air is just a blur.
David states:
This isn’t really a natural look, so now I’m gonna switch to second curtain sync. If I time it just right, I can have the blur happen first, when the shutter opens, and then the flash fires right at the end of her jump, this makes the blurry part trail behind her, and gives a more realistic looking sense of motion.
If your subject is moving then it’s probably best to stay with first curtain sync, so you know that the flash will fire right when you push the button. But for those times when you want to shoot with a slow shutter speed, and especially if you want to have those trailing lines behind your subject, then switch to second curtain sync, and fire away.
Watch the full episode with David Bergman and Adorama TV: