Flash triggering

[Graham_of_Rainham]

What is the best way to trigger flash units off the camera?

I've seen posted in threads that some slave units will not trigger the FLs as the voltage is to low too run the trigger. I've also heard that some old flash guns can damage the camera if connected to a PC hot shoe adaptor.

Any suggestions please

Graham

[snaarman]

Re: Flash triggering

FWIW, I have used both my Nikon SB28 and Vivitar 550 FD (99p off ebay!) with my Olympus 8080 and E-400 with no problems. These also both trigger using a light sensing slave from Hama. I knew they were safe to use because I measured the trigger voltages at 4 to 6 volts. No problem there...

However I avoided my another cheap flash units because their trigger voltages measured 85v. Not good for your camera.

So the answer is that there are lots of flash units that may well work, and just as many that might fry an unprotected camera. The only sure way is to measure the voltage between the centre pin and the the earth connection (usually on the side of the bracket where it contacts the camera flash mount bracket) To do this you need a cheap digital Volt Meter (DVM) .. A cheap DVM can be as little as £5 - which might be a smart investment if you want to buy 3rd party flashed of ebay.

Equally, you might be able to afford proper Olympus flashes, you might not be a cheapskate like me :-)

Pete

[Graham_of_Rainham]

Re: Flash triggering

Pete,

Now that's what I consider to be a comprehensive reply...
Sincere thanks.

I've got a DVM and will do just as you suggest. Could I please ask what Hama units you have used successfully?

Also anyone else, if you have used a slave unit to successfully trigger a FL50, can you let me know the make/model etc..

Graham

[photonutter]

Re: Flash triggering

I use a light cube, got from jessops. http://www.jessops.com/Store/s9094/0...y=False&comp=n
You use the built in flast to trigger so no problems there.

[snaarman]

Re: Flash triggering

Graham

Sorry, I don't recall which Hama it was.. It was a Christmas present and it doesn't have a model number on it.. However, it looks like this...



Pete

PS, in the spirit of this post I shot this image using my E400 and bounced flash from the SB28 :-)

[Graham_of_Rainham]

Re: Flash triggering

Pete,

That's brilliant, thanks a lot

FYI Measured the following voltages @ the contacts :-

Olympus F280 - 3.0v
Olympus FL50 - 4.65v
Sunpak 433D - 9.8v
Cobra RS10 - 190v
Olympus PS200 - 280v

So I guess I wont be putting my oldest Oly Flash onto my E-Sys Camera

Regards

Graham

[Naughty Nigel]

Re: Flash triggering

I may be too late replying, but....

All electronic flashguns charge a large value capacitor to a potential of 300 to 350 or so volts, which is then discharged over a period of a few µS through a glass tube containing xenon gas. Indeed, any electronic flashgun (including those in compact cameras) is capable of delivering a fatal electric shock.

The voltage at the flashgun terminals is determined by the triggering circuitry. Older cameras with mechanical flash contacts could safely handle high voltages and currents from simple flashguns without sustaining damage (even though the user was at risk of electrocution). However, modern cameras with solid state flash triggering can only handle low voltages and currents, and may also be sensitive to polarity.

Regarding remote triggering.......
Digital cameras fire their flashguns twice for each exposure.

When the shutter button is pressed, the flashgun fires a short, measured pre-flash to calculate exactly how much flash power is required. This is follwed a few milliseconds later by the main flash. Most remote triggering units are not capable of relaying this information to or from the flashgun, so when the master flash fires its pre-flash, the slave guns fire at full power. Not only does this completely discharge the slave flashguns; it also confuses the exposure system, resulting is severe under-exposure.

[Invicta]

Re: Flash triggering

I may be too late replying, but....


Regarding remote triggering.......
Digital cameras fire their flashguns twice for each exposure.

When the shutter button is pressed, the flashgun fires a short, measured pre-flash to calculate exactly how much flash power is required. This is follwed a few milliseconds later by the main flash. Most remote triggering units are not capable of relaying this information to or from the flashgun, so when the master flash fires its pre-flash, the slave guns fire at full power. Not only does this completely discharge the slave flashguns; it also confuses the exposure system, resulting is severe under-exposure.

Interesting info, sorry to jump in but I think this helps explain my experiments with a remote controlled FL50-R when using mirror lock-up on the camera.

When I press the shutter the camera pop-up flash sends a signal out and the remote FL50-R also gives a small flash. (is this FL50-R flash equivalent to the pre-flash?)

When the mirror lock-up time-out is reached then the pop-up flash fires again and the FL50-R now gives its full powered flash.

Mirror lock-up seems to be limited to about 4 seconds as any longer than this and the FL50-R will just fire all on its own after approx 4 seconds.

[Naughty Nigel]

Re: Flash triggering

Interesting info, sorry to jump in but I think this helps explain my experiments with a remote controlled FL50-R when using mirror lock-up on the camera.

When I press the shutter the camera pop-up flash sends a signal out and the remote FL50-R also gives a small flash. (is this FL50-R flash equivalent to the pre-flash?)

When the mirror lock-up time-out is reached then the pop-up flash fires again and the FL50-R now gives its full powered flash.

Mirror lock-up seems to be limited to about 4 seconds as any longer than this and the FL50-R will just fire all on its own after approx 4 seconds.

I'm not too sure how flash metering would work on an E3. I would assume the first (pre) flash occurs just before the mirror goes up, and the second fires a second or two later, when any mirror vibrations have died down?

I cannot see any problems with this, as long as the subject being captured doesn't change in the intervening period.

On a more conventional camera (like the E1 -which doesn't have Live View), the exposure system cannot work with the mirror locked up, as the light sensors are housed in the pentaprism.

[Invicta]

Re: Flash triggering

I'm not too sure how flash metering would work on an E3. I would assume the first (pre) flash occurs just before the mirror goes up, and the second fires a second or two later, when any mirror vibrations have died down?

I cannot see any problems with this, as long as the subject being captured doesn't change in the intervening period.

On a more conventional camera (like the E1 -which doesn't have Live View), the exposure system cannot work with the mirror locked up, as the light sensors are housed in the pentaprism.

Not sure of the E-3 flash metering either but the pre-flash before mirror lock-up would explain what I see happening.

You can set the mirror-lock to a wide range of time intervals I used to use 10 seconds, alas the main flash happens all on its own after 4 seconds so with remote flash you have use a much shorter mirror lock-up time.

[Naughty Nigel]

Re: Flash triggering

Not sure of the E-3 flash metering either but the pre-flash before mirror lock-up would explain what I see happening.

You can set the mirror-lock to a wide range of time intervals I used to use 10 seconds, alas the main flash happens all on its own after 4 seconds so with remote flash you have use a much shorter mirror lock-up time.

But does it still expose correctly?

TBH, I cannot see the point of mirror lock up with flash (as the flash will freeze any movement), or indeed mirror lock of more than a few seconds.

[Invicta]

Re: Flash triggering

But does it still expose correctly?

TBH, I cannot see the point of mirror lock up with flash (as the flash will freeze any movement), or indeed mirror lock of more than a few seconds.

With mirror lock-up it exposes OK if the mirror lock-up is less than four seconds as the signal from the camera pop-up flash causes the main flash to happen at the right time.

If mirror lock-up is say 10 seconds this is what happens

time 0, camera pop-up flash sends signal out, main flash gives pre-flash

time +4 seconds, main flash fires

time +10 seconds camera pop-up flash sends signal, main flash does nothing, picture under exposed.

I am puzzled by this but you have a valid point about the flash freezing any movement.

[Naughty Nigel]

Re: Flash triggering

With mirror lock-up it exposes OK if the mirror lock-up is less than four seconds as the signal from the camera pop-up flash causes the main flash to happen at the right time.

If mirror lock-up is say 10 seconds this is what happens

time 0, camera pop-up flash sends signal out, main flash gives pre-flash

time +4 seconds, main flash fires

time +10 seconds camera pop-up flash sends signal, main flash does nothing, picture under exposed.

I am puzzled by this but you have a valid point about the flash freezing any movement.

Indeed. I don't think I have ever used mirror lock up on my E1, although I have used it on other cameras.

The whole idea of mirror lock is to prevent vibration caused by the mirror flapping up and down during long (tripod mounted) exposures.

I would therefore suggest that using mirror lock up with a flashgun is not only unneccessary, but will also slow down the whole picture taking process.