Does Sigma's Flash fire twice for rear curtain?

ordinaryless · 7th April 2005

Hi guys,

Im using Sigma Super 500DG on my 300D. I realised when i'm using Rear Curtain Sync on my flash and i set my camera to slow shutter(0.5sec or longer), the flash actually fires off once when the shutter opens, and another time just before the shutter is closed.

Does anyone has similar experience or am i missing something here?

Splutter · 7th April 2005

Its the same even for Canon flash. Happens when you use ETTL. I think if manual mode it doesn't happen.

gryphon · 7th April 2005

Yes like Splutter said.

1st is the pre-flash (when ETTL used), which is used to calculate the actual flash power needed, the 2nd one is your actual flash to illuminate e subject.
When used without Rear Curtain Sync, e flash also flashes twice, it occurs in quick succession, very fast for us to notice.
ONLY E-TTL uses this pre-flash. When u change e flash settings to TTL or Auto or other modes, you'll get only 1 flash

ordinaryless · 7th April 2005

thanks for the explaination guys..

seems like the only way to get one flash is to use fully Manual Mode on the flash yeah?

mpenza · 7th April 2005

the first flash is only for calculating exposure. it should have no effect on the picture.

PhotoDog · 7th April 2005

Not too sure, will the first flash act as a red eye reduction?

HelmetBox · 8th April 2005

Originally Posted by ordinaryless

thanks for the explaination guys..

seems like the only way to get one flash is to use fully Manual Mode on the flash yeah?

yes

HelmetBox · 8th April 2005

Originally Posted by PhotoDog

Not too sure, will the first flash act as a red eye reduction?

depends.......

ordinaryless · 9th April 2005

the reason i want to get rid of the first flash is when i use slow shutter(1/2sec) in extremely low lighting condition, my subjects would thought the shot has been taken after the first flash is fired, hence they'll start to move away.. I'm just wondering if there's any easy way out like turning off the first flash so that i dun have one by one tell the pple im going to photograph to keep very still for the next 1/2 seconds.. Even after i've instructed them, some will still move after the first flash..haiz..

7th April 2005	#1
ordinaryless Member Join Date: Jun 2003 Location: East - West - East Posts: 885	Does Sigma's Flash fire twice for rear curtain? Hi guys, Im using Sigma Super 500DG on my 300D. I realised when i'm using Rear Curtain Sync on my flash and i set my camera to slow shutter(0.5sec or longer), the flash actually fires off once when the shutter opens, and another time just before the shutter is closed. Does anyone has similar experience or am i missing something here?

7th April 2005	#3
gryphon Senior Member Join Date: Jan 2003 Location: Dry cabinet! Posts: 1,708	Yes like Splutter said. 1st is the pre-flash (when ETTL used), which is used to calculate the actual flash power needed, the 2nd one is your actual flash to illuminate e subject. When used without Rear Curtain Sync, e flash also flashes twice, it occurs in quick succession, very fast for us to notice. ONLY E-TTL uses this pre-flash. When u change e flash settings to TTL or Auto or other modes, you'll get only 1 flash __________________ Dreaming... 14mm f2.8, 16-35 f2.8 mkII, 85 f1.2 mkII

7th April 2005	#2
Splutter Senior Member Join Date: Dec 2003 Location: Gim Boon Tai Posts: 2,819	Its the same even for Canon flash. Happens when you use ETTL. I think if manual mode it doesn't happen.

7th April 2005	#5
mpenza Moderator Join Date: Jan 2002 Location: New York City Posts: 13,397	the first flash is only for calculating exposure. it should have no effect on the picture.

7th April 2005	#6
PhotoDog Member Join Date: Nov 2004 Location: Tampines Posts: 136	Not too sure, will the first flash act as a red eye reduction?

9th April 2005	#9
ordinaryless Member Join Date: Jun 2003 Location: East - West - East Posts: 885	the reason i want to get rid of the first flash is when i use slow shutter(1/2sec) in extremely low lighting condition, my subjects would thought the shot has been taken after the first flash is fired, hence they'll start to move away.. I'm just wondering if there's any easy way out like turning off the first flash so that i dun have one by one tell the pple im going to photograph to keep very still for the next 1/2 seconds.. Even after i've instructed them, some will still move after the first flash..haiz..