1D mk3 second curtain setup

<p>I set up my menu option for second curtain and attached a 580 EX2. I found that the flash fired at the start of a 5 sec exposure and not at the end of the exposure, therefore second curtain failed. I then investigated the 580 manual and found that it had to be set up for 2nd curtain by pressing the H/>> button.<br>

My question is what's the purpose of setting the camera menu for 2nd, since setting the flash for 2nd with the camera set for 1st yields 2nd curtain?</p>

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<p>I found that the flash fired at the start of a 5 sec exposure and not at the end of the exposure, therefore second curtain failed.</p>

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<p>Are you sure it failed? All ETTL Speedlite pre-flash at the beginning of the exposure regardless of first or second curtain sync. Just test it with at trailing flash exposure in a dark room.</p>