How does a slave flash work?


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Tweek

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#1
ok this is a damn stupid question...I've never used a slave flash before, but I know of the underlying working concept, that it triggers off when it senses a flash from the master (or the internal flash).

But my question is, must the sensor of the slave flash be directly in front of the master? Or in other words, what position should the slave flash be in order for it to work?

Been surfing the net, got lots of info on slave flash, but none actually states the positioning of the slave.

Anyone can help?? Thanks.....
 

roygoh

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#2
Most slave flash are triggered by the infra red content of the master flash when it is fired.

So the answer really depends on the sensitivity of the slave flash triggering circuit, as well as the IR content in the master flash output.

If the overall sensitivity is good enough, then the slave flash does not always have to be in front of the master, because reflections off the wall or other objects would be enough to trigger the slave unit.
 

roygoh

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#3
Of course there are also other triggering method, such as using radio wave signals (some Canon and Minolta systems, I believe). Then you can place the slave flash anywhere you want, as long as it is within the range of the RF transmission.
 

Tweek

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#4
thanks roy..

in the case, let's say I'm in a public area shooting together with other photographers. There is a risk that my slave will be triggered by the flashes from the other cameras?
 

mpenza

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#5
Originally posted by Tweek
thanks roy..

in the case, let's say I'm in a public area shooting together with other photographers. There is a risk that my slave will be triggered by the flashes from the other cameras?
yup!
 

roygoh

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#7
Yeah, IR triggered slave flash is good when you are shooting alone. If you are shooting with other photographer, then you should either get RF triggering system or use a sync/TTL extension cord.

Imagine when some else take a picture, your slave flash fires also to mess up their exposure. You will be expelled immediately from the session! :bsmilie: :bsmilie:

Also, using IR triggered slave outdoors may be problematic also, as you do not have much reflection of the main flash from the surrounding, so there will be more restrictions on the placement of the slave flash.
 

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