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04-13-2010, 03:33 PM   #1
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second curtain sync problem K10D + AF360

Hi folks,

forgive my ignorance, But I'm trying to get to grips with second curtain sync on the K10D and my AF360FGZ.

I'm shooting in manual mode, slowish shutter speed to allow ambient light in, but I want the flash to fire at the END of the exposure to freeze motion. The problem I'm having is that there's always TWO flashes, one at the start of the exposure and one at the end too. See the example below, I know it's turd and handheld but it illustrates the principle, showing the two flashes when I only want the one.

I've set the flash in the camera settings to trailing curtain sync, and the same on the AF360FGZ, and even experimented with other settings but always the same effect..

Other posts seem to suggest that the first flash is supposed to be BEFORE the exposure, but it always seems to show up for me...

And before it's suggested, I've got the latest firmware, 1.3..

What am I doing wrong folks?

(I apologise for the blatant groinal gropage in this picture, he does it all the time, I think his condition should be given a suitable latin name then we may be able to get treatment for him..)

04-13-2010, 03:39 PM   #2
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i wonder if there is a bit of light left from using the flash in pttl mode? try using the flash on m mode and keeping it on trailing curtain synch. see if that does it!
04-14-2010, 12:34 PM   #3
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I'm going to move this to the DSLR section in hopes it might get more viewing.
04-14-2010, 06:10 PM   #4
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I canít be positive with out knowing the shutter speed but I donít see what looks like 2 flashes but one flash with a slow shutter speed.

To test this as you walk by a mirror take the same photo. As you are using second curtain in the mirror you should only see the flash from the second (with maybe a small amount at the beginning form the first flash decaying). You should be walking before you release the shutter. About the only time you should see the pre flash have an effect on the photo is in something like a mirror from the flash decay.

Unfortunately second curtain sync is only available with P-TTL.


04-14-2010, 06:38 PM   #5

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I don't think there were two flash strobes. There was only one.

You're correct that the pre-flash strobe in p-TTL occurs before the exposure, in fact, it happens before the mirror goes up (the mirror needs to be in the "down" position for the light to reach the light-meter sensors in the prism). To verify this yourself, set the camera in 2 sec delay mode. You'll see the pre-flash strobe, then mirror going up, then after 2 sec, shutter release.

I think the problem is that you want the ambient light to contribute to the exposure, while at the same time, you want the flash strobe to freeze the action. The ambient light illuminates the subject BEFORE the flash strobe, and the sensor will record that. If you hit the shutter release while the man is already in action, the photo may turn out OK. But if the man is standing, then the shutter opens, then he starts to jump up, then the flash fires, the sensor will record the man standing. And that looks like the flash strobe at the beginning of the exposure.
04-16-2010, 10:58 AM   #6
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Thanks for all the replies folks..

The shutter speed was 1/2 a second, at f/5.6, iso 100.

he was moving through the whole half a second, the first flash illuminated him starting to jump, the second in mid-air..

I'll try the mirror thing when I get chance and report back..Thanks for the suggestions folks...

04-16-2010, 11:04 AM   #7
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Soldbear, very interesting explanation.
04-26-2010, 01:10 AM   #8
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Thanks folks, I tried the mirror thing that DAZ suggested, and sure enough, the picture only contained one flash. So SOLDBEAR, you're probably right when you say that the first exposure is from the ambient light and the second is the flash..

There are DEFINITELY two flashes though, so what on earth is the pre-flash for? (again, forgive my ignorance, I'm really struggling with flash+ ambient light, the balancing act of exposing for both..)

04-26-2010, 01:22 AM   #9
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Ahh forget it, Just been reading some older threads about the difference between TTl and P-TTL, that answered my question adequately!

Good forum people, a real source of help, thanks!

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