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Flash for Optical TTL with Canon?


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#1 jgrjr777

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Posted 04 March 2012 - 06:52 PM

I have been thinking about a flash project for Canon 5DII and now 5DIII users. There are not many options for TTL with Canon. A few converters at best. No onboard flash to trigger optical.

I saw some forum members have developed some mini flashes to trigger optical TTL for various reasons. I thought what if I took a small Canon flash and cannibalized the electronics to reproduce the Canon ETTL signal the way an onboard flash does for 7D users. This would enable triggering optical TTL with a 5DII.

Right now my plan would be to use a compatible cable on the camera then hard wire it to the Canon electronics which would be placed somewhere in the housing. I would probably replace the flash tube with an LED that you would connect to an optical port that would replace an existing Nikonos 5Pin.

So far all I have done is buy the small Canon 270EXII for about $159.00 US.

Does this make any sense?

#2 bvanant

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Posted 06 March 2012 - 05:46 PM

I have been thinking about a flash project for Canon 5DII and now 5DIII users. There are not many options for TTL with Canon. A few converters at best. No onboard flash to trigger optical.

I saw some forum members have developed some mini flashes to trigger optical TTL for various reasons. I thought what if I took a small Canon flash and cannibalized the electronics to reproduce the Canon ETTL signal the way an onboard flash does for 7D users. This would enable triggering optical TTL with a 5DII.

Right now my plan would be to use a compatible cable on the camera then hard wire it to the Canon electronics which would be placed somewhere in the housing. I would probably replace the flash tube with an LED that you would connect to an optical port that would replace an existing Nikonos 5Pin.

So far all I have done is buy the small Canon 270EXII for about $159.00 US.

Does this make any sense?

Good luck, I think that controlling LED outputs is a bit more complex than controlling flash tube timing and that firing capacitor based loads through LEDs is not trivial. If you get it to work, I suspect there is a market if it doesn't recycle too slowly; most folks shooting electrical sync cords want a lot faster firing than you can get with an onboard flash
Bill

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#3 jgrjr777

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Posted 08 March 2012 - 01:16 PM

What I am talking about is using a Canon flash to trigger an optical TTL system like the Inon 240. This would work no different then it does with the 7D. Only it would be a Canon flash like the 270EX not the onboard flash on the 7D.

It would work something like this.

Reduce Canon 270EX to componenets that could fit in open areas in a housing. The 270EX is a small flash.
Then connect the 270EX components to the 5dMKII hot shoe with a Canon ETTL compatible cable.
Direct the flash output to a fiber optic sync port.
Use optical TTL on Inon 240s.

There would be no change to the flash electronics at all only the packaging. You would have to set the output very low to get quick recycle times.

One downside I see would not being able to turn this on or off the way you can with some Optical TTL compatible housings.

I only mentioned the flashtube being removed as it would not be needed. Some Wetpixel members have already built mini flashes that use LEDs that work fine. Forget the idea of replacing the flash tube with an LED. I agree that could be problamatic with capacitors dumping into the LEDs.

I will test the idea with the 270EX intact and a cable to see if I can get Optical TTL with my Inons. I do not see any reason this would not work.

Maybe I should move this to the project section where the other crazy people are? I would really like some more feedback.

#4 MIKE POWELL

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Posted 08 March 2012 - 03:13 PM

Great idea....I love when people think outside of the box!

If you shoot wide angle fast moving subjects even shooting with manual optical on the lowest output setting it's not as fast as shooting with hard wired cables.

If your shooting macro I say go for it!

Looking forward to hearing more as you progress.
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#5 DrAlex

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Posted 09 March 2012 - 01:19 PM

Hi all.

I do not wanna to discuss in this thread is needed TTL mode underwater or not. If that, I shoot in manual mode, the last 8 years.
I carried out experiments with system flashes Canon 580 EX II with Canon 5DmkII in a custom housing.
The first flash was managed and synchronization by electric cable (6 wires), and the second flash via an optical fiber (I use TosLink audio cable). Flashes as Sea&Sea YS 250 Pro and Inon Z240 did not work in TTL mode. They fires only in Manual mode with the optical synchronization.
Next step was when I use the system flashes - Canon 580 EX II and Nissin 866 pro mk II.
I was able to flash in e-TTL mode as a clear mining on the master flash on the cable wire, and on the remote flash unit via optical cable. Custom Housings for system flashes was without any control buttons.
I operated of all modes of the two flashes via the camera menu.
It was really great.

#6 bvanant

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Posted 21 March 2012 - 12:14 PM

What I am talking about is using a Canon flash to trigger an optical TTL system like the Inon 240. This would work no different then it does with the 7D. Only it would be a Canon flash like the 270EX not the onboard flash on the 7D.

It would work something like this.

Reduce Canon 270EX to componenets that could fit in open areas in a housing. The 270EX is a small flash.
Then connect the 270EX components to the 5dMKII hot shoe with a Canon ETTL compatible cable.
Direct the flash output to a fiber optic sync port.
Use optical TTL on Inon 240s.

There would be no change to the flash electronics at all only the packaging. You would have to set the output very low to get quick recycle times.

One downside I see would not being able to turn this on or off the way you can with some Optical TTL compatible housings.

I only mentioned the flashtube being removed as it would not be needed. Some Wetpixel members have already built mini flashes that use LEDs that work fine. Forget the idea of replacing the flash tube with an LED. I agree that could be problamatic with capacitors dumping into the LEDs.

I will test the idea with the 270EX intact and a cable to see if I can get Optical TTL with my Inons. I do not see any reason this would not work.

Maybe I should move this to the project section where the other crazy people are? I would really like some more feedback.

That might work but is a little different from your first post where you said you would replace the flash tube with LED. This way might work but I think packaging will be tough. Great concept if you can figure out how to mount the flash tube to the camera. Let us know how it goes.
Bill

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#7 Balrog

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Posted 21 March 2012 - 01:36 PM

The flash power is developed and controlled by duration. If you set the output very low to get short cycle times TTL is out of the window.
I think the one of the few ways to do this is to dispense with the flash tube & capacitor, keep the front end TTL electronics and use its fire and quench signals to operate an LED.