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Subject: "Technical - how does wireless TTL work?" Previous topic | Next topic
Paul_Fisher Gold Member Awarded for his multiple article contributions Charter MemberSat 03-Nov-01 01:06 PM
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"Technical - how does wireless TTL work?"


Perth, AU
          

I've been reading the various posts about the SB-28/SU4 and SB-50 etc being used as wireless slaves with TTL metering. Question: How does the camera send the quench command to the remote flash? I can see that a sensor on the flash itself will trigger the flash to fire, but the quench part of the equation has me puzzled.

I'm currently using an F-80 with a third-party (cheapo) hot-show flash, but would like to move up to a proper speedlight setup.

Paul Fisher
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Paul Fisher
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Replies to this topic
Subject Author Message Date ID
Reply message RE: Technical - how does wireless TTL work?
jrp Administrator JRP is one of the co-founders, has in-depth knowledge in various areas. Awarded for his contributions for the Resources
03rd Nov 2001
1
Reply message RE: Technical - how does wireless TTL work?
Paul_Fisher Gold Member Awarded for his multiple article contributions
03rd Nov 2001
2
     Reply message RE: Technical - how does wireless TTL work?
jrp Administrator JRP is one of the co-founders, has in-depth knowledge in various areas. Awarded for his contributions for the Resources
03rd Nov 2001
3
          Reply message RE: Technical - how does wireless TTL work?
jjussi
03rd Nov 2001
4
               Reply message RE: Technical - how does wireless TTL work?
Paul_Fisher Gold Member Awarded for his multiple article contributions
03rd Nov 2001
5

jrp Administrator JRP is one of the co-founders, has in-depth knowledge in various areas. Awarded for his contributions for the Resources Charter MemberSat 03-Nov-01 04:11 PM
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#1. "RE: Technical - how does wireless TTL work?"
In response to Reply # 0


San Pedro Garza García, MX
          

Well, the fun part about the SB-50 is that in fact it has an integrated built-in SU-4. So it improves upon the effective GN for cameras like the N80.
Another option is to use a SC-17 cord with any Nikon speedlight, which will render an even larger effective GN.
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Paul_Fisher Gold Member Awarded for his multiple article contributions Charter MemberSat 03-Nov-01 09:42 PM
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#2. "RE: Technical - how does wireless TTL work?"
In response to Reply # 1


Perth, AU
          

Thanks, JRP, but that doesn't answer the question

What I was trying to ask was: How does the SB50 or SU4 know when enough light has been emitted? With the cord connection, or the flash in the hotshoe, the camera sends a signal to the flash saying "Start firing now". When the camera's meter determines that there is sufficient light on the subject, it sends a second message saying "OK you can stop now". This is easy enough when there is a cable connection, but how does it work in wireless mode?

I understand that the SB50 or SU4/SB28 can be used as the remoe, and triggered by the pop-up flash of the F80. But how do they receive the "turn off" signal?

Thanks again
Paul Fisher
My home page
Engineering, music, instrument making, photography and family history

Paul Fisher
Nikonian in Perth, Western Australia
My home page

  

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jrp Administrator JRP is one of the co-founders, has in-depth knowledge in various areas. Awarded for his contributions for the Resources Charter MemberSat 03-Nov-01 09:47 PM
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#3. "RE: Technical - how does wireless TTL work?"
In response to Reply # 2


San Pedro Garza García, MX
          

Of course that did not answer the question.
I am running some tests with my SU-4's to be absolutely certain. TTL is possible, that I know, however, the ISO speed is not "sent" from the camera, for example. I'll let you know as soon as I do for sure.
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JRP (Founder & Administrator. Nikonian at the north-eastern Mexican desert) Gallery, Brief Love Story, The Team
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jjussi Basic MemberSat 03-Nov-01 10:27 PM
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#4. "RE: Technical - how does wireless TTL work?"
In response to Reply # 3


KLAUKKALA, FI
          

I am not sure but... Simples answer is, because it trickered by another flash, it stop when that "tricker" flash is stopped.

1. Tricker flash fires
2. SU-4 notice that and fires slave
3. When there is enought light on film Tricker flash goes off
4. SU-4 notice that light "flow" is reduced so it knows that tricker has gone so it must close slave flash too...

--
© Jussi Jääskeläinen from Finland
All picture what are posted to www.nikonians.org

© Jussi Jääskeläinen from Finland
All photos posted to nikonians

  

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Paul_Fisher Gold Member Awarded for his multiple article contributions Charter MemberSat 03-Nov-01 10:39 PM
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#5. "RE: Technical - how does wireless TTL work?"
In response to Reply # 4


Perth, AU
          

Jussi, you're right! I found the information on this page: http://www.maxwell.com.au/support/faq/11001_SU4_JW.html

which is a subset of the SU-4 FAQs at Maxwells in Oz:
http://www.maxwell.com.au/PHOTO/ACC/Nikon-acc/SU_4_FAQ.html

Thanks
Paul Fisher
My home page
Engineering, music, instrument making, photography and family history

Paul Fisher
Nikonian in Perth, Western Australia
My home page

  

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