firing the flash at the end of te exposure instead of the beggining...

[nagoshua]

I've lost the instruction manual to my 430ex flash, im going out to take some photo in town tonight of a friend so ill need a slow shutter for the background and some flash to expose him, question 1, when is it best to fire the flash in this situation? before or after? and question 2, how do i get my flash to fire at the end of the exposure (im guessing its a custom function on the flash or something).

 

[Big Mike]

IMO, it's almost always best to fire the flash at the end of the exposure...known as 2nd curtain or rear curtain sync. This way, any motion blur will show up behind the flashed exposure...and look more natural.

That being said, if you use 2nd curtain sync...there will be a longer time between flashes. The camera/flash uses a pre-flash for metering...usually this is so fast that it's almost indistinguishable from that actual flash...but when you push the flash to the end of the exposure...the pre-flash still fires before the exposure. This may cause your subjects to think that the first flash is the real flash and turn away...or it may cause them to blink etc.

I'm pretty sure you can set 2nd curtain sync on either the camera or the flash. I'm not sure which will be the overriding control...the camera I think.
It's one of the custom functions in your camera's menu.

 

[Jeff Canes]

Did you check the Canon site to see if you can download the manual

 

[nagoshua]

i thought it was that, i tried it and the flash still fired at the beggining, turns out i have to set it on both camera and flash, problem is, i dont know which custom function on the flash it is!!

 

[Big Mike]

From HERE

Enabling second curtain sync.

This depends very much on the camera and flash unit that you’re using. Early on, Canon put control for this feature on the flash unit. Later they switched to putting control for this feature on the camera body. So whether you have second-curtain sync available to you depends on a complicated set of permutations.


Many mid to high end Canon flash units, listed below, have a button or switch which lets you enable second curtain sync. It’s usually marked with a triple triangle ( >>> ) symbol or the word SYNC. For instance, on the 430EZ and 540EZ you press the + and - buttons together simultaneously to turn on second-curtain sync. When you do so a triple triangle symbol appears in the LCD. On the 300EZ and 300TL there’s a small slide switch - left is first-curtain sync and right is second-curtain.


Most midrange and professional EOS bodies from the A2(E)/5 onwards have a custom function that lets you specify whether you want first or second curtain flash. The exception is the original Elan/100, which had a custom function that can only control the internal flash and not external flash units. In the case of a camera with a custom function and an external flash unit which has a second curtain switch then you use the physical switch on the flash to control the function.


Low-end EOS cameras, such as the 1000 series or Rebel series, do not have any custom functions and so cannot control second curtain sync options directly. So to take advantage of second curtain sync on such cameras you must have an external flash which has externally-available controls to operate it.


Second-curtain sync cannot be used with any EOS camera in a PIC (icon) mode - you have to be set in P, Av, Tv or M modes. And you can’t set second-curtain sync in stroboscopic mode or FP mode, since that wouldn’t make any sense. Finally, second-curtain sync requires a dedicated Speedlite flash unit - it isn’t supported on flash units connected via a PC socket (see PC connector section below).

List of which flash units and camera bodies have second-curtain sync.


Note: verifying this information is difficult, since it’s not listed on all product specs, and I don’t have access to every camera and flash unit that Canon have ever built. I believe this list is accurate, but please let me know if there are any errors.


Flash units which do not support second-curtain sync:
Speedlites 160E, 200E, 480EG, ML-3.


Flash units with external second-curtain sync controls:
Speedlites 300EZ, 420EZ, 430EZ, 540EZ, 540EZ, 430EX, 550EX, 580EX, 580EX II, MR-14EX, MT-24EX.


Flash units which can use second-curtain sync when used with any EOS body that has a second-curtain sync custom function other than the Elan/100:
Speedlites 220EX, 380EX, 420EX, 430EX, 550EX, 580EX, 580EX II, MR-14EX, MT-24EX.


Camera bodies which cannot support second-curtain sync in any form:
EOS EF-M, 750, 850.


Camera bodies which lack custom functions altogether and so support second-curtain sync only when used with flash units with external controls:
EOS 650, 620, 700, all EOS 1000 series cameras, all EOS Rebel film cameras, all EOS Kiss series cameras, 300, 300V, 500, 500N, 5000/888, 3000/88, 3000N, the IX Lite/IX 50/IX 7*, IX**, EOS 300D/Digital Rebel/Kiss Digital***.


Camera bodies with custom functions but which lack a custom function to enable second-curtain sync:
EOS 600, 630, 1, 1N, 1NRS, RT, 10/10S.


Camera body which has a second-curtain sync custom function that works on the internal flash but not on external units:
EOS Elan/100.


Camera bodies with custom functions that enable second-curtain sync on both internal flash and on compatible external flash units:
EOS A2(E)/5, Elan II(E)/50(E)/55, Elan 7(E)/30/33/7, D30, D60, 10D, EOS 350D/Digital Rebel X/Kiss Digital N, 20D/20Da, 30D, 400D/Digital Rebel Xti/Kiss X Digital.


Camera bodies with custom functions that enable second-curtain sync on compatible external flash units but which lack internal flash:
EOS 3, 1V, 1D, 1Ds, 1D mark II, 1Ds mark II, 1D mark IIN, 1D mark III, 5D.


The T90 camera and the 300TL flash unit support second-curtain sync, but only with each other.


* I haven’t been able to find out if the IX Lite/50/7 camera supports second-curtain sync with flash units that have external controls, but since it’s based around Rebel-style technology it seems unlikely that such support would have been removed.


** The Westfall/Overton FAQ states that the IX can use second-curtain sync with 380EX flash units, which lack external second-curtain sync controls. The Canon “Flash Work” brochure, however, isn’t clear on this.


*** Out of the box this camera does not have custom functions and thus cannot use second curtain sync unless the flash unit has a second curtain sync switch. However, enterprising users have found a way of enabling hidden custom functions on this camera by reprogramming its firmware. If you choose to do this you can enable second curtain sync on this body

 

[nossie]

Kudos to Big Mike for doing the research work.

 

[Big Mike]

That is from what is commonly referred to as 'The EOS Flash Bible'. It's a lot of reading, much of which is rather technical...but all the info is in there, somewhere.