Guide Numbers and sync speed in flash.

[robski]

I managed to get the older EX380 off e-bay for £60 mark - It's not the best speedlite but it works well. Some of the Canon fits may fire ( like the Jessops ones they are flogging off cheap) but the exposure is all over the place. The EX380 gives reliable results.

[wolfie]

Another thing to watch out for is the trigger voltage, many of the older type have a trigger voltage far higher than required for DSLS. This could result in "Frying" to cameras electronics.

Have a read here. http://www.botzilla.com/photo/strobeVolts.html

Harry

[Don Hoey]

I have been on a trawl of the net to try and understand Canon Flash Systems and came across this. It has got to be the most comprehensive guide to the Canon system on the net. A lot of reading here. It does list EOS system compatible flash units for those looking to attach the flash to the camera as opposed to remote triggering.

http://photonotes.org/articles/eos-flash/

Don

[John]

Don, a most absorbing and instructive set of flash pictures. I have a Vivitar 283 and a Canon 430ez. Do you know whether or not either of these would fry the 20D electronics if used on the hot shoe? I normally use them with slave flash.

[Don Hoey]

Originally Posted by John

Don, a most absorbing and instructive set of flash pictures. I have a Vivitar 283 and a Canon 430ez. Do you know whether or not either of these would fry the 20D electronics if used on the hot shoe? I normally use them with slave flash.

John,

The Vivitar 283 most certainly WILL fry electronics. The trigger voltage is too high. OK if used off camera and triggered by a slave. I will have to check for info on the canon 430ez.

Don

[Don Hoey]

John,

Canon 430ez does appear to be OK. Here are a couple of links to Canon EOS flash units

http://www.kjsl.com/~dave/speedlites.html

http://www.bobatkins.com/photography...c.html#3flash0

http://photonotes.org/articles/eos-flash/

That lot should give some reading.

Don

[John]

Originally Posted by Don Hoey

John,

Canon 430ez does appear to be OK. Here are a couple of links to Canon EOS flash units

http://www.kjsl.com/~dave/speedlites.html

http://www.bobatkins.com/photography...c.html#3flash0

http://photonotes.org/articles/eos-flash/

That lot should give some reading.

Don

Thank you Don I will read them to night got to go out in 15 minutes.

John

[John]

Originally Posted by John

Thank you Don I will read them to night got to go out in 15 minutes.

John

Don, I am back now. Thank you again for those informative links. I have now had chance to read them and here is the relevant information that I have gleaned. The trigger voltage on the later Vivitar 283 flashguns is 5 volts. The earlier models have a higher voltage but the actual value was not stated. However, I learned that it appears as a constant voltage across the positive and negative contacts of the hot shoe, so I was easily able to measure it on my particular model and it is 8 volts. Canon EOS cameras use 5 volts so the trigger voltage on my Vivitar 283 is too high for constant use. It seems then that I was wise to always trigger it with a slave unit.



John.

[Don Hoey]

Although there are good deals on old flash units to be had, the electronic circuits in modern cameras will, as John says, be fried by the high trigger voltage of old but useable by remote triggering flashguns.

I have found this listing to show how high some of the trigger voltages can be http://www.botzilla.com/photo/strobeVolts.html

The moral is definately IF IN DOUBT CHECK.

Do not poke around inside these things without knowledge, they contain high voltages

Don

[Saphire]

Originally Posted by Don Hoey

Although there are good deals on old flash units to be had, the electronic circuits in modern cameras will, as John says, be fried by the high trigger voltage of old but useable by remote triggering flashguns.

I have found this listing to show how high some of the trigger voltages can be http://www.botzilla.com/photo/strobeVolts.html

The moral is definately IF IN DOUBT CHECK.

Do not poke around inside these things without knowledge, they contain high voltages

Don

I agree with that Don, don't poke. Many, many, many years ago I did and nearly blew my fingers off. The capacitor is lethal.