Saturday 31 October 2009

One radio transmitter and three triggers for £40. What a bargain for Keith Robins Photography!
Amazon is the place to visit for a fast efficient service. I ordered the triggers on Wednesday and, even though there was a Post Office strike in action, the packet was delivered on Friday. the Vivitar 285HV flashgun which I ordered the same day came a couple days later, well packed and in good nick. Thank you to the postmen for what I term a pretty good service in your hour of strife.
How do the triggers handle in use? Brilliantly!
The normal place for a radio transmitter is in the hotshoe along with a trigger mounted beneath a remote flashgun - this arrangement fired one of my Vivitar 285HV's at up to 50 metres, a lot further than the advertised 30 mtrs. I was more than pleased with this result.

For the next test I added an optical slave into the chain, just to explore the limitations. One Vivitar on the camera, then at 30 metres distance the radio transmitter was slotted into an £8 optical slave, a second 285HV was then slotted into one of the three triggers and placed an additional 30 metres from camera. The equipment all works together just fine, which is fantastic!

Next, I wanted to know whether a flash in ETTL mode would operate the remote flash. I placed a Canon 550EX in ETTL mode on top of a Canon 5D, which in turn was set to manual. The optical slave was connected directly to the Vivitar 285H. This system failed miserably!
A flashgun in ETTL mode, or a pop-up flash, sends out a small pre-flash before the shutter opens to calculate the strength of flash exposure needed to light the main subject. Of course this pre-flash will also set off the remote flashgun operated via an optical slave unit before the shutter is open. When the main light fires a few milliseconds later it's too late for your remote flash as it has already gone off and is still in the process of recharging.

Maybe this is why some photographers, new to the world of flashguns can easily be lead into thinking that multiple flash is beyond them, especially as their images consistently portray dead flat lighting from the on-camera flash.

Fear not, there is a way around this most irksome problem!
You may have noticed that when taking a photo a half press on the shutter button causes focusing / exposure info to pop up on screen for about 15 seconds.
The trick with using an ETTL flash as a master to fire remote flashes on radio triggers is to half press the shutter button to bring up this information, then press the star button which fires the tiny pre-flash along with the remote slave flash. Meanwhile the shutter is still closed.
Now wait about 10 seconds, but no longer than 14 seconds, before fully pressing the shutter button to take the photo proper. If you're using newish batteries this should be long enough for the remote flash to recharge and both guns will now fire while the shutter is open and give whatever power you have set on them.

However, when the on-camera flash is set to manual there is no pre-flash and both guns will fire as one light without any trouble.
I also tried using aperture priority and it worked great.
Carrying out the same test using shutter priority I found that the Canon 5D limited the speed to 1/200th with the end result coming out spot on.
All this exploration took several hours and I'll need to repeat this type of testing a few more times before it sinks in - remember I'm new to ETTL and the Canon 5D as maual flash has been my staple diet since the early seventies.
Hope this is some help in your flahs photography - Keith Robins.