Doug Kerr
June 15th, 2006, 08:05 PM
We often have questions about using the Speedlite 550EX flash unit as a "dumb slave", optically triggered by, for example, a studio flash system. A common motivation is to use it as a background light or hair light.
If we try to do this with a widely-owned optical slave trigger unit, the basic Wein hot shoe type (type HS), we find it won't work. The 550EX is fired by the first burst from the studio lights, but then the system "locks up", and subsequent bursts will not fire the 550EX.
I presume that the E-I (voltage-current) curve of the sync input of the 550EX, after triggering, does not allow the SCR that is probably used in the Wein unit to "extinguish".
[Note to those who may wish to verify this by testing (I did after it had first been reported to me): with the system "locked up", if we give the Wein a "close range" burst from another flash, it will trigger the 550EX.]
I recently bought two of the Wein Micro Slave ("Peanut") trigger units (Type PN) for various uses in my studio configuration. It occurred to me that these doubtless have different components, and perhaps different circuitry, than the familiar HS unit, and perhaps they would not be susceptible to this "lockup" phenomenon.
I rigged up a test (I didn't have the proper adapter for the flash end so I had to be creative) and sure enough, the Peanut will reliably trigger my 550EX repeatedly.
So if you want to try this (no guarantee it will work on your 550EX, of course), what you would need is:
1. Wein "Peanut" optical slave unit:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=63118&is=REG&addedTroughType=search
2. "Flash end" PC cord to hot shoe adapter:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=95414&is=REG&addedTroughType=search
The Peanut slave has a prong that is functionally equivalent to the camera's PC terminal. It should plug into the PC plug on Item 2 above.
I have no idea how all this applies to the 580EX.
If we try to do this with a widely-owned optical slave trigger unit, the basic Wein hot shoe type (type HS), we find it won't work. The 550EX is fired by the first burst from the studio lights, but then the system "locks up", and subsequent bursts will not fire the 550EX.
I presume that the E-I (voltage-current) curve of the sync input of the 550EX, after triggering, does not allow the SCR that is probably used in the Wein unit to "extinguish".
[Note to those who may wish to verify this by testing (I did after it had first been reported to me): with the system "locked up", if we give the Wein a "close range" burst from another flash, it will trigger the 550EX.]
I recently bought two of the Wein Micro Slave ("Peanut") trigger units (Type PN) for various uses in my studio configuration. It occurred to me that these doubtless have different components, and perhaps different circuitry, than the familiar HS unit, and perhaps they would not be susceptible to this "lockup" phenomenon.
I rigged up a test (I didn't have the proper adapter for the flash end so I had to be creative) and sure enough, the Peanut will reliably trigger my 550EX repeatedly.
So if you want to try this (no guarantee it will work on your 550EX, of course), what you would need is:
1. Wein "Peanut" optical slave unit:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=63118&is=REG&addedTroughType=search
2. "Flash end" PC cord to hot shoe adapter:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=95414&is=REG&addedTroughType=search
The Peanut slave has a prong that is functionally equivalent to the camera's PC terminal. It should plug into the PC plug on Item 2 above.
I have no idea how all this applies to the 580EX.