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Old Jun 7, 2004, 11:23 AM   #1
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Hi Folks,

I've been given a slave unit for a flash. It's very cheap, no name on it, and no instructions. Having searched this forum I've found out about some cameras having a preflash, which will trigger the slave. Can anyone tell me if my camera does?

Many Thanks

Gareth
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Old Jun 7, 2004, 1:57 PM   #2
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I have no idea if your camera does preflash, but good chance that it does , in which case, a "cheap" slave flash won't work.
However you can do simple test(s) to find out:
- Set your camera in "Fill-in Flash" mode, and observe the flash, normally, you can notice 2 or more burst if it preflash . ( in the "Red-eye reduction" mode, it preflash for sure)

or :
- Simply take the same indoor photo (room) with the slave off, then another with the slave on, if theslave flashwas triggered by the camera's preflash , then your 2 photos are identical ( meaning your slave flash is useless with this camera, save it for another (future) usage:?)


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Old Jun 7, 2004, 2:02 PM   #3
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Thanks for the info.

With the slave the picture becomes very dark, with just the internal flash the picture is how you'd expect. Not sure what this means.

Gareth.
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Old Jun 7, 2004, 2:32 PM   #4
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Gareth,
Yeah, It means that the slave is useless .

In fact, at the preflash, the camera … well, preflash:-) , then measure the light reflected by the subject , the goal is to adjust itself for the next flash burst (the good one).

Since the slave is triggered by this preflash, it burst out, and "add more light" , the camera than think that it's own flash is too strong for the circumstance , and prepare to make a weaker flash for the right moment, and this time of course, the slave can not burst another one because it doesn't have time to recharge . The photo was then taken with the camera flash adjusted less than normal correct exposure.

Hum … I just try … not sure it's clear enough :?

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Old Jun 8, 2004, 5:53 AM   #5
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Makes perfect sense!

Thanks for your help!
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Old Jun 9, 2004, 8:56 AM   #6
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For my Olympus (C-700) I use the Metz 34-CS2 Digital slave flash which works fine with the preflash (this is a flash with a slave built-in that can work with either single or preflash cameras). The only downside of the flash is it runs on two CR2 lithium batteries (which aren't cheap). Here's a shot I took in the store to test if the flash handles the preflash of my Oly:

http://img4.photobucket.com/albums/0...n/preflash.jpg
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