What is a Master and Slave?

[jamesino]

Ironically, I have been unable to find a definite answer to this on Google.
What exactly is a Master and Slave strobe set up? Is it a set up where the master strobe acts as the primary light source and the slave strobe acts like a fill light and does kind of like the job a light reflector does?

 

[peterbj7]

No, not exactly. The master is the triggering flash, directly switched under user control, and the slaves simply react to whatever the master did. Yes, in practice the slave will be used off-camera to provide indirect lighting, in the same way that a reflector can sometimes be made to do. In fact, sometimes the master is blocked from illuminating the subject, so its only job is to trigger the slaves. Just as with car brakes, the master cylinder receives your control input (your foot) and the slave cylinders at the wheels simply respond to whatever the master did.

 

[kundalini]

This can be a touchy subject. See [video=youtube;mOCsNrzlV2k]http://www.youtube.com/watch?v=mOCsNrzlV2k"]here[/video].

If you insist, an alternative is [video=youtube;DuifqpgpHe0]http://www.youtube.com/watch?v=DuifqpgpHe0"]here[/video].

 

[jamesino]

thanks. What is this master and slave ratio? Is the ratio of light intensity between the two?

 

[peterbj7]

No fixed ratio, depends on the equipment used and its placing. I've used slave flashes as far as 40ft away from the primary/master, but I had to ensure the light reaching the slave was sufficient to trigger it. Remember it's effectively line-of-sight.

 

[kundalini]

My experience has been with the Nikon CLS flash system. The on-board flash can act as the Commander and optically trigger (up to 3 groups) of off-camera flashes. I'm not sure what you are asking of the ratio of master to slave intensity. I generally use the on-board as the Commander only to trigger the other strobes. Meaning the the on-board flash does not illuminate the scene, but optically triggers the off-camera strobes to fire. I generally set them (off-camera strobes) to the intensity that I want. TTL is okay, but I have better results when set in Manual mode.

As an example just today.... see here. I was trying to have a black background (flash falloff) while having the subject well illuminated. Seemed to have worked.

Apologies for the first post, just havng a laugh.

 

[peterbj7]

the the on-board flash does not illuminate the scene, but optically triggers the off-camera strobes to fire

How exactly? Is it visible light or something like IR? I've achieved this by simply masking off the on-board flash so minimal light goes forward, while trying not to restrict the light going sideways to the slaves. But it's always a bit hit-and-miss.

 

[K_Pugh]

The on board flash doesn't illuminate the scene as it fires before the shutter opens. The reason i know is is because i've tried using an older SB-22 with an optical slave sensor adaptor fitted and it fires too early and doesn't have an effect on the exposure.

 

[Groupcaptainbonzo]

Very basically the MASTER strobe is fired by the photographer (Usually by the camera). The SLAVE is fired by the Master. Positioning, power ratios et al is /are set by the photographer in order to achieve the results that he/she requires.
Have a look at this. it will blow your socks off.


http://strobist.blogspot.com/2006/02/welcome-to-strobist.html

 

[Jedo_03]

http://www.prostudiolighting.com/Beginning Studio Lighting.htm

Considering the basic nature of the OP's question - I'd not be suggesting he try anything as fancy as firing the slaves from 40ft away - nor masking off the master/trigger light source... My 'master' isn't even a light source - it happens to be a wireless trigger...
James - my advice is to do some background reading - search this forum or google, find out all you can...
Jedo