Apr 02 2009
The Joys of Rear Curtain Flash!
I’ve done quite a few lighting tutorials here on Yanik’s Photo School, especially using off camera small flashes like the SB-900 or the 580EX II. I love these little buggers and the more I use them, the more dust accumulates on my big studio strobes. And today’s lesson will be about an in-camera feature that most DSLRs have called Rear Curtain Flash.
I discovered this camera feature a long time ago with my Nikon D70 when I wanted to shoot a long exposure of a moving car at night. The built-in flash popped at the beginning of my 3 second exposure so the light trails went “through” the car. Not what I wanted. I needed that flash to go off at the end of my 3 second exposure so that the light trails would be behind the car. So I went through my manual and found this lovely feature called Rear Curtain. 
After purchasing and reading The Moment It Clicks by one of my favorite photographers, Joe McNally, I discovered the logic behind rear curtain flash and that’s what I’ll try to convey to you in this lighting tutorial.
What is Rear Curtain Flash?
By default, your camera is set to front curtain, which means your flash fires at the beginning of the exposure, when the shutter opens. As mentioned above, rear curtain is getting your flash to fire at the end of your exposure, just before the shutter closes.
Ok, you’re probably saying: “that’s just fine and dandy Yanik, but what’s the difference whether the flash goes off at the beginning or the end of the exposure?” Well, you won’t see a difference at high shutter speeds but you will at slow shutter speeds. Remember what a flash does. It lights up your subject and “freezes” it in time. So if your flash goes off at the beginning of the exposure, you’ll freeze your subject and then the movement for the rest of the exposure will blur right over your “freeze” and it won’t look natural or sharp. If your flash goes off at the end of the exposure, the blur comes first and then…. BLAM! You freeze your subject right at the end making it sharp with all the blur “in background” of your frozen subject. Take a look at this example of a dancer. This is a 1 second exposure, hand held, in rear curtain mode and she was moving pretty fast. You can see in the 100% crop of her face how the sharpness was kept.
When to use Rear Curtain Flash?
All the time! No kidding. Really. My camera has it set to rear curtain since I read The Moment It Clicks. It was just that “aha!” moment. Think about it for a second. Let’s say your shooting at 1/250 sec. you’ll agree that whether your flash fires front or rear curtain, it won’t make any difference. But it will make a difference if you’re shooting at 1/15 sec. So why bother keeping it in front curtain mode?
Not convinced yet? Let’s say you’re at a wedding shooting indoors and it’s quite dark. You have your trusty SB-800 or 580EX II on your camera, set to default front curtain, and you’re shooting in Aperture Priority (A) mode. What’s your slowest shutter speed? Go ahead check. You can check it with your built-in flash as well, it’ll be the same. So? Yup, you got it. You can’t go below 1/60 sec. in P or A mode. Why? The camera’s smart and doesn’t want you to make blury photos, that’s why. What will happen at 1/60 sec. in a dark room? A properly exposed subject (by the flash) and a completely dark background loosing all the ambiance of the party.
If your camera is set to rear curtain, you can be in any mode (P, A, S /Tv and M) and the camera will adjust to the ambient light then fire the flash at the end of the exposure.
Here’s another example of rear curtain flash at a party this summer. I wanted to create a dynamic photo so I shook my camera during the 1 second exposure. As you can see, even while shaking my camera, the dancers came out pretty sharp!
To sum it all up: front curtain = BAD rear curtain = GOOD. Ok, ok, that’s pushing it a bit, I know. I’ll say it this way:
- Front Curtain flash = having a sharp subject then smugged over it by movement blur
- Rear Curtain flash = having blurry movement then with a sharp subject over it
So keep your camera on rear curtain and you’ll thank me for it!
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Excellent explanation. I’ve heard of people talking about rear curtain flash but never bothered looking it up to see what its good for. I shoot mainly in my studio and always complained about shooting in low light situations like at dinner events and parties. Now it’ll get interesting. Thanks.
Yanik,
Thanks so much for this quick, easy, and helpful tip. I’ll be setting mine to permanent rear curtain flash also.
Nice, i didn’t even know that a picture can be taken this way – i mean – to get a sharp subject and blured backgroud. Excellent Yanik,thanks.
Thank you sir!
hi Yanik,
thanks for all your works, really fantastic.
I’ve a question that struggles my mind since age: is it possible use the rear curtain flash also if I shot with radio triggers?
I shot with a Canon 40D, 580EXII shooting with Elinchrome Skyport.
It seems not working in any way!!
Please, anyone can help me
anyone can help me please?
Hi yanik, so can this be achieved when working with nikon c.l.s or when using pocketwizards thanks. and Thankyou for all the great post and information on your site
@ Desmond
Yes and yes.
Does this only work when you have the 580ex ON the camera? I believe that is why emmepi14 is having trouble.
Debbi
FYI: Many of the canon dSLRs (IIRC Digital Rebel Xt and older at least) only honor “Rear Curtain Flash” when using the built in flash. When using an external flash, they trigger it at the beginning of the exposure..
-Jason
emmepi14,
You’ve got to set the flash mode in your camera to rear mode. It works for me with my Nikon d70s.
suge
Hi,
I am not an experienced photographer, and I’m new to the ‘Rear Curtain Flash’ aspect, not knowing of it before reading theses great articles of Yanik’s. I have a Sony a200 DSLR. I can find no reference about ‘Rear Flash’ Can someone tell me if I have the option, and if so how I access it please.
Many thanks,
Edward
Interesting … I just read the same book and was google’ing how to do it. It’s a very good book by the way ..
I love your explanation and examples, thanks!
Nice explanation of the concept, thanks. Maybe you could add that a curtain is actually the shutter which opens and closes when photo is taken.
There are two curtains covering camera sensor– First opens when you click shutter button, and after a period of time equal to your shutter speed, the second curtain follows the first, thus closing the shutter/exposure. You guessed it, the first curtain is called the front and second is rear curtain. So rear curtain flash fires when the second curtain is closing.
This is for those who did not know what a curtain was. Just wanted to throw it out there.
Thanks
I have a canon EOS 450d (Rebel XSI). Under flash control, I’ve set my “shutter sync” to second curtain. However, when I tested this out by taking a picture in shutter priority at 1 second, the flash went off both when the shutter opened, and when it closed. I expected it to go off when the shutter closed – should it also do so when it opens? I think I might get the same result…?
Excellent advice! I’ve always liked this look but never thought ot leave it in that mode permanently..duh! Thanks!
Hi, I have a nikon d90 and I tried rear curtain flash mode. I set 1 second like shutter speed, f/4 as aperture and I put my camera on a tripod, then my friend shot the photo while I’m moving my hand in front of the camera lense. The problem is that in the picture I cannot see the blur motion of my hand, and then the sharp on but there’s just one transparent hand. Anyone can help me?
OK … as a newbie, how do you set this on a Nikon D5100? Any advice is appreciated.
Just found this as well, great article.
just came across this article, big thank you!! very easy explanation the difference between front and rear curtain. greetings from Poland