1st or 2nd Curtain Sync - can someone explain?

[Sean Dempsey]

on the 10D, there's a custom function for shutter syncing to the 1st or 2nd curtain. Can someone explain what this means, and does this have anything to do with flash? thanks.

[Kokopeli]

That I shoot Nikon so I'm familiar with their lingo, but here's what the difference between 1st and 2nd curtain is..

1st cartain fires the flash at the beginning of the exposure or when the shutter opens. 2nd fires it at the end, just before the shutter closes. In Nikon terms this is known as Front sync and Rear sync. We also have a feature know as Slow sync which allows us to shoot flash photos at the slower shutter speeds instead of the 1/60 second or faster default setting.

Hope this answers your question.
~Brian

[kamboura]

Here is my understanding of it from a purely technical point of view, and I would like to ask the more experienced members to validate the following statements and hopefully provide examples.

Curtain sync has to the with the exact momemt that the flash fires compared to the opening of the shutter. On 1st curtain, the flash would fire as soon as the shutter opens, and on 2nd curtain, it fires as it closes.

When is this usefull: If you are for example using a fill flash, on a moving object, with a slow shutter speed. The subject would have a trail in the picture. In case of 1st sync, the begining of the blur would be the brightess (because the flash was fired at the instant), and the the rest is fading. Thus it would look like the blur is leading the subject. In case of the 2nd curtain, the last instance of the subject on the film would be the brightest, thus the blur would seem to follow the subject a la speedy road runner kind of effect.

Again, this is my book knowledge, I would like someone who actually knows what they are talking about to confirm

[kamboura]

Sorry Kokopeli, didn't mean to repeat what you said, you replied as I was writing my response. I am glad we said the same thing though.

[another view]

With Nikon, Slow Sync = 1st curtain and Rear Sync = 2nd curtain.

The other replies are correct, the flash fires at either the beginning or end of exposure - obviously used with a slow shutter speed. You might use 1st curtain when trying to get a blurred shot - shoot when the person is in the spot you want them (the flash fires now to create a sharp image of them) but then you get blur and background light after that.

Second curtain might be useful when you want to get a sharp posed shot of people but still get some light into the background. People will usually hold still until they see the flash go off, then they'll move. Since you're exposing for the background first, that's what you'll get.

Nikon had a shot in a brochure or instruction manual that shows a motorcycle going by. Shot with 1st curtain, the light trails from the tail light go thru the bike and towards the front of it. With 2nd curtain, you get the light trails extending from the back of the bike away from it. I guess you could do it with 1st curtain but the motorcycle would have to be going backwards...

[Kokopeli]

I was going to give the same example you did, but I ran out of time.. I had to get my son to baseball practice! Thanks for building upon my response!

~Brian