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womblegs Jun 7, 2004 11:23 AM

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


KCan Jun 7, 2004 1:57 PM

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:?)

womblegs Jun 7, 2004 2:02 PM

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.


KCan Jun 7, 2004 2:32 PM

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 :?

womblegs Jun 8, 2004 5:53 AM

Makes perfect sense!

Thanks for your help!

Mikefellh Jun 9, 2004 8:56 AM

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:

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