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Slave Flash Trick


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#1 rstark

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Posted 04 March 2002 - 04:41 PM

This should help out a lot of you that use your on-board flash to trigger your slaves. Instead of hooking up fiber optic cables, using weird semi-transparent shields, etc. you can use a little trick that makes your internal flash invisible to visible light spectrum but will still trigger your slaves. It turns it into an IR trigger.

You take a piece of unexposed but developed slide film, cut out a piece a little bigger than the cameras flash and tape it over the cameras flash with the emulsion side out. To find the emulsion take a razor blade and scrape both sides. The side with the emulsion will scrape off easily. You want the emulsion side out because your cameras flash generates heat and the emulsion will eventually stain your flash window. It will not do this if the base side (non emulsion side) is facing the flash. Use black electrical tape or any other black tape that can take a little heat to tape the piece of film over the cameras flash. Set your camera to force flash, turn on your strobes to slave setting, take a picture and poof all your strobes fire. Some visible light will show through the film that covers your cameras flash but not enough to worry about. Also you can set your cameras internal flash to its minimum setting to conserve battery power and generate less internal heat. This all works by passing IR infrared light through the piece of slide film but very little visible light. If you don't shoot any film cameras go to a good photolab and ask for a tail end of a DEVELOPED piece of s lide film. Hope this helps.

________
Robert

#2 meister

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Posted 04 March 2002 - 08:41 PM

Thanks for the tip!!!!! Sounds like a great method of blocking the internal flash, easily applied as well as easily removed for topside photos with the camera out of the housing. I'll try it out next trip, June.
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#3 David

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Posted 07 March 2002 - 10:39 PM

Thanks for this tip.

I was thinking of placing a plastic mirror/white strip within my housing to deflect the light upwards. This will strike the TTL sensor. But your idea is a lot easier.

I have yet to try it, but your idea is technically sound and practical.

Thanks!!!

#4 herbko

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Posted 15 March 2002 - 03:20 PM

Great Idea. I spent an hour or so trying it out last night.
I've posted my results in a reply to another discussion

http://www.wetpixel....ead.php?tid=145

This is better than reflecting the light up since the sensor on the
YS90DX faces the front of the strobe. This should be more reliable.

Now that I thought a little about it. The pre-flash could be an advantage
in this scheme, it keeps your strobe from being set off by other photographers
near by. Does anyone know how long is the "memory" of the YS90DX?
That is how much time can elapse between the two flash and still have the
strobe triggered. Maybe I'll try some tests this weekend.

Now if only the weather would cooperate so I can try this out on a dive.

Herb
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#5 herbko

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Posted 25 March 2002 - 10:55 AM

Finally got to dive with my new lighting setup.
Two YS90DX both on slave mode synced to the built-in flash
filtered with a piece of unexposed slide.
Strobes were set to the "Pre" and slave mode.

It worked !

I had tested it all indoors and it had all worked,
but when I tried it at the parking lot just before the
dive, it didn't trigger! I was a little concerned.
I thought about it a moment and realized the bright
sun light probably saturated the strobe sensors.
Tried it again in a dark area in my car and the strobes triggered.

Jumped in, and eveything works. Even the shots at 10' depth triggered.

I'll post some shot when I have the time to upload.

Herb
Herb Ko http://herbko.net
Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro