Canon Digital Photography Forums  

Go Back   Canon Digital Photography Forums > 'Equipment Talk' section > Small Flash and Studio Lighting
Register Rules FAQ Members List Search Today's Posts Mark Forums Read

Thread Tools Display Modes
Old 20th of May 2006 (Sat)   #1
Join Date: Jun 2003
Posts: 102
Default optical trigger

I just bought an optical trigger to use with a 420EZ flash. It will fire once properly if I fire a flash with my 550EX. After that, though,it does not fire again unless I turn the flash off or take the trigger off and put it back on. Am I missing something? I have tried all the setting I know (full manual) etc. Is this how they are supposed to function?
ahmadof is offline   Reply With Quote
This ad block will go away when you log in as member
Old 20th of May 2006 (Sat)   #2
Cream of the Crop
PacAce's Avatar
Join Date: Feb 2003
Location: ABE, PA USA
Posts: 26,804
Default Re: optical trigger

Nope, you're not missing anything. Evidently, the Canon Speedlite flashes have some current flowing through the hotshoe after it's been fired. Other flashes that work fine with optical triggering units do, too, but the current flowing through those is not as high as that of the Speedlites. The characteristic of an SCR (Silicon Controlled Rectifier, which is the component in the trigger unit that basically acts as an electronic switch turned on optically) is that once it is triggered, it will stay turned on for as long as the minimum holding current required to keep the SCR turned on is flowing through it. So, the net effect of the higher current flowing through the Speedlite hotshoe is that the SCR does not turn off. If it doesn't turn off, then you can't trigger it again to fire the flash until you disconnect and then reconnect the flash or turn off the flash and then turn it back on again.

I just spent an hour and half this afternoon with my Speedlite connected to my home made optical trigger with a digital multimeter connected across the sync wire and ground (to mearure voltage) and an analog VOM connected in series with the sync wire (to measure the current through the sync wire). That's how I came up with the above observation.
PacAce is offline   Reply With Quote
Old 20th of May 2006 (Sat)   #3
Join Date: Jun 2003
Posts: 102
Default Re: optical trigger

wow, thanks. I guess all optical triggers won't work then. I was going to try one of the more costly ones (i have a$14 ebay one). Which is a shame as I think that was the only peice of the puzzle keeping me from going pro
ahmadof is offline   Reply With Quote
This ad block will go away when you log in as member
Old 20th of May 2006 (Sat)   #4
Curtis N
Master Flasher
Curtis N's Avatar
Join Date: Apr 2005
Location: Northern Illinois, US
Posts: 19,130
Default Re: optical trigger

See if you can pickup an old flash unit at a camera shop, pawn shop or wherever. Better if you can get one with variable manual settings. They usually go pretty cheap and most will work fine with a slave trigger.
"If you're not having fun, your pictures will reflect that." - Joe McNally
Chicago area POTN events
Flash Photography 101 | The EOS Flash Bible | Techniques for Better On-Camera Flash | How to Use Flash Outdoors | Excel-based DOF Calculator
Curtis N is offline   Reply With Quote
Old 21st of May 2006 (Sun)   #5
Join Date: Oct 2005
Location: Santa Clarita, CA
Posts: 116
Default Re: optical trigger

I had the exact same problem with my 420 and optical triggers, fortunately I have several old flashes that will work just fine with them. Still, I wish the 420 would work, but at least thanks to PacAce's description above, now we know why they won't work more than once. That was the part that always confused me, why they would fire one time correctly, but never again unless you turned it off and then back on.
"Knowledge, Sir, Should Be Free To All"
Harcourt Fenton Mudd--- I, Mudd
RLRiley is offline   Reply With Quote
Old 22nd of May 2006 (Mon)   #6
Cream of the Crop
akiwi's Avatar
Join Date: Jun 2005
Location: Munich, Germany
Posts: 6,856
Default Re: optical trigger

Metz has an optical trigger that works.
I tried it out at my local camera store a few weeks ago and it worked perfectly. Other tests with Hama triggers didn't work.
akiwi is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Homemade optical slave trigger shakin360 Small Flash and Studio Lighting 17 13th of May 2010 (Thu) 12:04
Optical Trigger drisley Small Flash and Studio Lighting 15 31st of January 2006 (Tue) 00:59
Optical trigger for studio lights tim Small Flash and Studio Lighting 4 16th of April 2005 (Sat) 03:09

All times are GMT -5. The time now is 03:35.

Powered by vBulletin® Version 3.6.12
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
This forum is not affiliated with Canon in any way and is run as a free user helpsite by Pekka Saarinen, Helsinki Finland. You will need to register in order to be able to post messages. Cookies are required for registering and posting. HTML in messages is not allowed, plain website addresses are automatically made active by the board.