580ex 2nd curtain

[canonboy]

Okay thanks for all your help with teh 2nd curtain getting light trails.
This is my result.

http://img170.imageshack.us/img170/6351/ltimg1130yw0.jpg

[PacAce]

That's very nice but you could have gotten the same picture using 1st curtain sync, too, I'm sure. :)

[canonboy]

Erm according to everyone else on this forum, no for various reasons I forget

[René Damkot]

Not everyone else: I agree with PacAce.
Furthermore: It would have been easier to get the timing right.

[canonboy]

I'll try get the reasons, but most people said to avoid 1st curtain

[chris clements]

What Renee & PacAce are implying (I believe) is that youve posted a picture that doesn't demonstrate the effects - any type of synch would've worked in that shot. All the movement is in one plane and there's no obvious cues as to the 'correct' direction of movement (the circular motion could be clockwise or anticlockwise without phasing the viewer), so it's immaterial which curtain.

Which curtain you synch to only matters where the viewer expects a particular direction of movement (like runners/bikes moving forwards), where first curtain synch will give light trails that give an unnatural impression (the runner/biker will appear to be going backwards)

[ToyTrains]

I'll try get the reasons, but most people said to avoid 1st curtain
With 1st curtain sync, the flash is fired at the beginning of the exposure (when the 1st curtain is fully open), while with 2nd curtain sync the flash is fired at the end of the exposure (when the 2nd curtain is about to close).

When you have a subject moving across the frame, the effect will be very different.

With 1st curtain sync, the subject will be lit by the flash and then the ambient light will be recorded for the rest of the exposure. With 2nd curtain sync, the ambient light will be recorded for the exposure and at the end the subject will be lit by the flash.

With 1st curtain sync any light from the moving subject (such as headlights on a car) will appear to to come out in front of the moving subject. With 2nd curtain sync any light from the subject will appear to come out of the rear of the moving subject.

The feeling of movement appears "normal" when lights appear to follow the subject which is achieved by 2nd curtain sync.

In your picture, the circular movement of the lights with no movement of the subject would not benefit by 2nd curtain sync.
hth,
Dan

[rabidcow]

I vote first curtain. That way you can frame and freeze your subject and then move the camera around while that shutter is dragging.

[chris clements]

I vote first curtain.

In this example, or generally?
If the former, it doesn't matter
If the latter, for most scenarios I disagree. You'll have all your cars/bikes/runners going backwards !!!

[Curtis N]

This page from Canon's Flashwork (http://web.canon.jp/Imaging/flashwork/functions/curtain/index.html)online brochure illustrates the effects of 2nd curtain sync.

Canonboy - ty it both ways yourself to see what works.

[canonboy]

mm i'll try first next time, and see what i prefer :)