Second curtain flash issue.

bass_junkie83

bass_junkie83

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I have a canon 400d with a 430ex flash and have recently learnt how to activate second curtain flash on it so i decided to take it along to a party over the weekend and try it out. One thing i noticed though that i though weird, even on second curtain flash i still get the first flash, so one at the start and one at the end of the exposure.

In most cases this wasn't a problem and i got results i'm pretty happy with.

VWAct09-369.jpg


VWAct09-370.jpg


VWAct09-394.jpg





But in some cases i ended up with double images. Here is an example of one, it's not terrible as the real bad ones i haven't hosted. But i end up with the first image burnt in, the blur in between and then the second image resulting in people with two heads.

VWAct09-389.jpg



It it possible to stop the first flash burst?
 
That first burst of flash is just a metering flash which measures the flash exposure and happens before the shutter opens anyway.

The movement in the last pic seems to be confined to the girl on the right, so I'd say it's definitely down to her moving during the ambient exposure and before the flash fired.

Depending on what your shutter speed is (how slow) you will get this and it's often best to ask your subects to keep as still as they can during slow sync exposures. It' sa bit difficult at a party where everyone is bombed though. :D
 
You'd have the same problem regardless of whether you used first or second curtain sync in this situation - it would just be a question of whether the blurring occured after the flash fired (1st curtain sync) or before it fired (2nd curtain sync).

Dunno if this helps at all, it hopefully gives more idea of situations where 2nd curtain sync would be an advantage...

CLICK
 
Oh right i see, I didn't think of metering.
So the ones where i got two main images are probably down to technique, or lack of. Maybe i held the camera still for a bit before moving, (i was going for the 'turning the camera' effect).

Thanks for your help. :)
 
It's not necessarily anything you've done wrong. What shutter speed were you using?
 
Half a second on most of them.
The 'bad' image i put up doesn't show too well what the problem was. Imagine there being a lot more distance between the two faces of the girl on the right of the last image with nothing in between, that's what i was getting.

I'll see if i can dig out a better example this evening.
 
You got some good results anyway and you're always going to get a few binners with stuff like this - luck inevitably plays a part in it.
 
Yeah, the double image is down to you pausing before you rotated the camera. If the pre-flash is distracting your subjects with second curtain sync, switch back to normal first curtain when the pre and main flashes go off so close together to don't notice it.

First or second curtain sync makes no difference to the effect you're after in situations like that - the trick technique that is working for you is slow-sync flash, dragging the shutter.

You can get rid of the pre-flash by switching the gun to manual, but then you'd lose all flash metering control. Manual exposure setting would be a nightmare in that situation.
 
I think you should be happy with those :thumbs:

As Hoppy says, it's dragging the shutter which is what you are doing. First or second curtain flash is only deciding which side of the flash (in time) that the ambient light is allowed to create the effect. However, there will be some times in normal first curtain flash that the swirly light effects would look odd/in front of the subject. I'd stick with second curtain I think, unless the pre-flash is bothering the subjects.

Look good to me :)

I especially like the second image. It looks like the light is spilling out of the cup (almost)
 
V8burble said:
I think you should be happy with those :thumbs:

As Hoppy says, it's dragging the shutter which is what you are doing. First or second curtain flash is only deciding which side of the flash (in time) that the ambient light is allowed to create the effect. However, there will be some times in normal first curtain flash that the swirly light effects would look odd/in front of the subject. I'd stick with second curtain I think, unless the pre-flash is bothering the subjects.

Look good to me :)

I especially like the second image. It looks like the light is spilling out of the cup (almost)
Click to expand...

Or you can reverse the direction in which the ambient blur moves by rotating the camera in the opposite direction.

The important thing, whether the flash fired first or last, is that the space in the frame where the main subject is positioned gets no ambient exposure on it. Or you'll get ghosting whether to you use first or second curtain sync.
 
HoppyUK said:
Manual exposure setting would be a nightmare in that situation.
Click to expand...

If you're the same sort of distance from small groups of people for each shot it's not a problem.
 
photon said:
If you're the same sort of distance from small groups of people for each shot it's not a problem.
Click to expand...

What do you mean by the same sort of distance? The OP looks very close, and if you're shooting three feet away, then on manual just a foot closer will be a more than a stop over exposed.

bass_junkie83 said:
These were all taken in manual. :)
Click to expand...

Can't be manual flash, or you wouldn't have got the pre-flash. Manual camera control maybe, but using E-TTL auto to match the flash output with the lens aperture.
 
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