Quote:
Originally Posted by robski
Just out of interest have you noticed if these get triggered on pre-flash or not. I used to have one of these 25 yrs ago. heavens knows where it is now. I think they rely fairly high flash trigger voltage to get their power from. I bought a secondhand flash last year which has a 5 Volt trigger voltage which I currently use with a long PC lead. I'd often wondered if it would work with one of these optical slave triggers.
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Rob,
The answers from some testing done tonight.......
I have two flashguns,
1. A National (Panasonic) PE-2057 with a >300V trigger voltage. This is my old film camera flashgun that cannot be used on a modern digital camera without destroying it. It is non-dedicated to a particular camera brand/fit with two "auto" power levels and a full power manual setting. This flash is normally used as a slave, triggered by an optical trigger module similar to that shown by Stephen above.
2. A Sigma EF500 DG ST with a 5V (I think) trigger voltage. This can be safely used on a digital SLR, and also an old film camera - I've just checked this by using it on my K1000, there's backwards compatibility for you. This gun has a fully auto P-TTL mode which utilises a pre-flash pulse for metering, plus two pre-set power levels available for manual flash use.
In addition to these, I have the pop-up module built into my dSLR (Pentax *ist DS). This uses a pre-flash pulse for metering when Program mode, Tv, or Av modes are selected. If full manual mode is set on the camera, there is no pre-flash pulse.
So, the first experiment was to trigger the National flashgun, using the optical slave, activated from the pop-up. As Lello has already said, this does not work if there is a pre-flash pulse; the pre-flash is enough to trigger the module and the remote flashgun does not then synch with the main flash discharge when the shutter is open. When using the camera in fully manual exposure mode, there is no pre-flash pulse and the National flashgun synched perfectly when triggered by the discharge from the pop-up.
The National flashgun was then replaced with the Sigma unit, the Sigma was attached to the optical trigger module and the Sigma set to the low power manual discharge mode. I figured that as the optical trigger had only a single contact on it, there was no point setting the Sigma to P-TTL mode as there would be no communication between trigger module and gun. The Sigma would discharge in synch with the pop-up with the camera set to manual exposure, but only if the pop-up was very close (<300mm) to the optical module.
The same experiment was repeated, using the "Test" button to force a discharge from the National gun, this being used to trigger the Sigma mounted on the optical trigger module. With its higher output (GN28), this was able to trigger the optical module at a reasonable distance and cause the Sigma to discharge.
The results of this testing:
Any pre-flash from the pop-up flash on a camera, or, based on previous experience, a pre-flash from the Sigma in my case, will cause the optical module to trigger the remote slave at the wrong time.
If it is possible to set the camera to not use a pre-flash (try using fully manual exposure mode), then it is possible to get a synchronised flash discharge using an optical trigger module.
If the flashgun on the optical trigger module is an old fashioned model with a high trigger voltage, then it is very easy to get the optical module to trigger the discharge of the remotely mounted gun.
If the flashgun on the optical trigger module is an modern model with a low trigger voltage, then it is necessary to put a lot of energy into the optical module to trigger the discharge of the remotely mounted gun. If you are using the pop-up flash built into your camera, this may not have the required power to trigger the optical module at a realistic distance.
If you have a high powered flash, this can be used to trigger a modern flash mounted onto an optical module at a realistic distance, though this will still be a lot lower distance than can be achieved with a high trigger voltage remote flash.
I've now got spots in front of my eyes from looking at flashguns discharging, so I hope this helps somebody.
Regards,
Duncan