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mauijon · Joined: 02 Mar 2005 Posts: 4286 Location: Maui, Hawaii

I used to do long exposures with a flash showing light streaks from vehicles. I always used 2nd curtain synch so the streak was behind the moving vehicle (instead of in front as with 1st curtain synch). Then I usually just left the camera setup for 2nd curtain for any and all future flash shots with no problem.

I've always wondered: Why aren't cameras automatically synched to the second curtain instead of making me select it? After all, regardless which curtain is synched, anything faster than maybe 1/30 sec shutter speed gives the same result with either curtain synch. So, I don't see any advantage to the first curtain synch.

Is there some rare, esoteric use for 1st curtain synch to which we peons are not privy?

Mike Price · Joined: 06 Jun 2008 Posts: 2920 Location: South Wales

As I understand it the only advantage of first curtain sync is that the preflash used to autofocus often causes the subject to blink. With first curtain sync the two flashes as very close together so you catch the exposure before the blink,with second curtain and slow shutter speeds the subjects eyes can be closed when the main flash fires.

Mike

mauijon · Joined: 02 Mar 2005 Posts: 4286 Location: Maui, Hawaii

Yes, I agree with what you say. But at normal shooting speeds with flash, it seems like either way would have a short duration between pre-and main-flash.

jeffbanke · Posted: Fri Oct 14, 2011 11:29 am

Jon, this is quite good explanation
http://neilvn.com/tangents/2010/06/02/first-curtain-sync-vs-rear-curtain-sync/

mauijon · Joined: 02 Mar 2005 Posts: 4286 Location: Maui, Hawaii

Jeff, thanks for the link. I see that if I use TTL with pre-flash, the 1st curtain usually works best. But if I'm NOT using TTL (non-TTL flash or flash on Manual)or if I use fast shutter speeds (125-200) then either curtain synch seems to work the same.