Just a quick question... I know the benefit of using second-curtain sync mode when dragging the shutter to create a light trail behind a "frozen" subject... Really cool!

I am not seeing why there would be a need for "normal" flash. Why would you ever need to take it off the second-curtain sync mode? When would a normal flash setting be better? Am I missing something here???!

Often times you'll want to freeze the action or use a flash to properly expose your subjects, but you want to leave the shutter open to bring the background light up so it is not underexposed. If you used second curtain sink, you may miss the moment you were trying to capture. It's a shame the setting is burried away in the Custom function menu. It would be nice to switch back and forth a little easier.

mike - using second curtain sync does not mean you need a LONG exposure, it simply means that the flash goes off at the end of the exposure. i shoot between 1/10th and 1/20th/sec exposures during wedding receptions due to dark lighting, using 2nd curtain sync and never have the feeling that i'm "missing the right moment" due to longer exposure times....

also, how is 2nd sync buried in menus? you hit a button on the 580 flash twice and you're in 2nd curtain sync mode... works every time.

I didn't know you could change the flash to 2nd curtain sync, that's cool. I'll have to try it out. I totally agree that at 1/20th or 1/20th you wouldn't miss the moment, I guess I was thinking more of artsy shots. Letting the background lights blur or a movement shot. Good point.

A little example from my most recent wedding. Not the best image, but it goes to show how second curtain can make an otherwise boring image much more exciting. The following image was shot with my Canon 1Ds Mark II, ISO 1600, 1/20th @ f/2.8

This is a good question. I prefer to use 2nd curtain synch for 90% of my shots.
However, If I am shooting formals I don't want to risk getting a blur because I want these to NOT look artsy as I feel the parents & family members who mostly buy these will not appreciate my artistic treatments.
Otherwise, I love the effect.

I guess i don't understand why using 2nd curtain synch would ever CAUSE blur...because if the flash is just firing at the end of the exposure, it doesn't seem to me like it would affect overall blur at all, just the LOOK of the blur (if there is blur at all due to a slower shutter speed). So even for formals, I don't understand why it would be a disadvantage to use 2nd curtain synch if your shutter speed is set fast enough for the formals...

Does that make sense at all? It did in my head

Maybe I am missing something obvious here...

Nice shot Trevor... That's exactly what I was thinking of.

+1

So, Trevor any insight into my question?

Or anyone else?--This is really bugging me!

2nd curtain sync doesn't cause blur. It's just that 2nd curtain sync is usually used when you are using slower shutter speeds. If you're shooting at 1/125th or faster you aren't going to have much blur, and you really aren't going to be able to tell the difference between 1st or 2nd curtain sync.

Thanks Beau that's definitely what I was thinking!

Hi Katie,
This is a good discussion. As mentioned earlier, you won't see a difference if you are shooting at a reasonably fast shutter speed. You will however notice a difference if you are shooting at around 1/30 of a second or slower. The difference you will see is the location of the blur in relation to your subject. Using front curtain sync will cause the motion blurring to occur in front of the subject while 2nd curtain (rear curtain for you non Canon shooters) will case the blurring to occur behind the subject.

If my explanation didn't make sense, here is one I found at http://www.camerapedia.org/wiki/Flash_sync which might make more sense.

Front Curtain Sync:
Generally, the flash sync fires at the instant the front curtain has fully opened. This is called front curtain sync, and it is used where it is desired that the flash freeze motion at the beginning of the exposure. Front curtain sync is adequate for most flash-photography. When making long exposures while also firing a flash, front curtain sync creates an effect where any motion blur - from ambient light - appears ahead of the subject, i.e. it appears to leave the subject behind. In the case of a moving motor vehicle in a night scene, for example, this can create an unrealistic effect since its headlamp and tail-lamp trails will extend out in front of it.

Rear Curtain Sync:
Some cameras offer the ability to fire the flash at just before the second curtain closes. This is called rear (or second) curtain sync, and it is used to freeze motion at the end of the exposure. When making long exposures while firing a flash, rear curtain sync creates the effect of motion blur trailing the main subject

Hope this helps clear the muddy water.

Regards,
Ryan

I understand the difference between 1st and 2nd curtain sync...but my question was: why would you ever really WANT or NEED Front Curtain Sync? What is the ADVANTAGE of using it versus rear curtain.

If at a slow shutter speed the effects of rear curtain are cool (and way better to me) and at a fast shutter speed, both yield the same effect, why would you ever take it off rear curtain sync?

Ahhhh.... I see. I agree... sorry for being so confused.

No that's ok!

well, for one, you can't highspeed sync using second curtain, at least using canon's ETTL/ETTL II system...

otherwise, i dont have a good, solid answer for you, but i'll stick with using rear/2nd curtain for slower shutter speeds/darker ambient light situations.

1++ on Trevor: No Highspeed sync possible. For me, the only reason not using 2nd curtain sync.

Mario