Initial requirements discussion

Moderator: seaton


Postby Gordon » Sun Sep 23, 2007 2:32 pm

Something that popped in to my head. If this is an open source project, there's no need to fall along company lines. So we could certainly support both the canon and nikon protocols. Going further though, is possible to support both at the same time ? I.e., pull together these, so that a Canon camera could remotely control a nikon and canon flash, both doing correct TTL ?

Is there enough overlap in the protocols to be able to bridge that gap ? Now that would be something novel that this project could do.
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Postby Thonord » Sun Sep 23, 2007 10:17 pm

Am working on a draft proposal for a protocol that will that will not be vendor spesific.
With all due respect for Nikon and Canon, I want to include Oly.
And if that means doing it my self, so be it.
Will I succede? Dont know, but am trying.

And dont worry, the key word is proposal.

Ppl who agree need normally not reply, those who disagree or have questions do.
Or - just ignore me.
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Postby seaton » Mon Sep 24, 2007 8:20 am

I would like the project to be as vendor neutral as possible and have our own protocol, while we can certialy plug in some vendor specific devices to our units, but our units would bridge our protocol to theirs. That way we might be able to have a multitude of different vendor devices hanging off our units, and they all talk together.

I'm looking forward to seeing your draft - awesome.
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Homer Simpson algorithm - remote slaves for all cameras

Postby feralfoto » Mon Sep 24, 2007 10:09 am

How about the Homer Simpson algorithm, 'Light goes on - light goes off' aka LGO-LGO

So, with a bit of hacking inside a powerful flash (Vivitar 283 or 285, who cares if you blow up a $25 flash?), it should be possible to turn the flash off remotely. Then, for the interface, pop a PE cell in front of the built-in flash (SLR, compact, anything except macnesium powder), hook it onto a radio and, LGO-LGO.

What is achieved?

If the built in flash goes
__---__---------__ (pre flash for exposure measuring)

then the slave goes

__---__---------__ (pre flash for exposure measuring only brighter)

likewise red eye, focus assist etc

1. Hopefully (maybe) iTTL, CLS, E-TTL will all work, because the camera only sees reflected light, so it shouldn't care if we have a slave following the camera exactly.

Of course, the PE cell attachment to the built-in flash would have to be light tight to prevent it spilling out and spoil TTL metering.

2. works with anything from a $100 compact (or phone!) to top of the line SLR

3. cant be made obsolete.

If the radio traffic is fast enough for handshaking or one way to the flashes, multiple flashes can be used.

So, does anyone else out there think it might work?

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Multiple TTL flashing

Postby Thonord » Mon Sep 24, 2007 11:05 am

I'm not sure if I follow you feralfoto. That said, my mind goes into overload when I try to envision TTL with multiple flashes.

Anyway, in the true Strobist spirit, I'm not looking for a photograph perfectly and evenly illuminated from every angle. I want to be able to control the flash levels.

Ppl who agree need normally not reply, those who disagree or have questions do.
Or - just ignore me.
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Postby feralfoto » Mon Sep 24, 2007 11:37 am

I'll try to explain my thinking using the example of a typical SLR built-in flash (GN = 12 in meters @100ISO) which I will call BI and my Vivitar 283 (GN ~ 35) which I will call 283

Scenario 1, BI knows nothing before the preflash, ie there is no focusing information used in the calculation of exposure (might be wrong there, and my entire arguement falls over). Say we are at 3m from the subject, then the preflash is (presumable) very brief, say 1/10,000 sec and it suggests the exposure is f4 (GN/distance = f stop, 12/3=4). It then fires for a typical 1/1,000 sec to give the exposure.

Scenario 2, BI is completely covered with a shroud containing a photo-electric detector (PE) which is connected to the radio transmitter and the radio receiver is integrated into the circuit of the 283. The BI fires its preflash into the shroud containing the PE which triggers the transmitter. 283 is also fired by the receiver for the same(ish) 1/10,000 second pre-flash, but it is a lot stronger, so the amount of light registering on the SLR sensor is also greater and the camera now thinks that the exposure should be f11 (35/3=f12, close enough to f11). When the BI fires into the shroud for the second time (for 1/1,000 sec) to take the exposure, the 283 fires as well (for 1/1000 sec) and you get a properly exposed picture at f12, ie TTL exposure control for the venerable 283 :wink:. Of course, if there were two 283s slaved for both the pre-flash and the actual flash, the exposure would be calculated and then taken at f16.

What it really depends on is getting the 283 to turn on and then off perhaps no later than 1/50,000 second after the BI turns on and off.

I hope that makes it clearer. I think my Homer algorithm will work but my electronics aren't up to the task, so I welcome this forum and I welcome feedback as well.

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Postby MQ » Mon Sep 24, 2007 5:08 pm

Well, since all flavors of TTL (no matter which brand) render
average results under average conditions.....

Usually I try to make all my results and settings as repeatable
as possible, which means (M)aster mode.

Even if I am off to some extent, I will be able to correct the
whole bunch of images with the same corrections in batch mode.

So, TTL doesn't really happen in my requirements.
Vice versa, I am more the Kalashnikov type.
Ugly, but working. Guaranteed.
If you are not part of the solution,
you are part of the problem.
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Re: e-TTL & CLS

Postby Kmount » Wed Jan 21, 2009 2:48 am

Does anyone have any information on Pentax TTL (either flavor TTL or P-TTL) as far as protocol/pins/timing? Are there similarities in the mechanisms (ie cows have lungs, deer also have lungs - even if not interchangeable they are structured similarly and provide similar function). One of my wishes is for a TTL translator. AF500FTZ is pretty reasonable pricewise now. That might change if everybody could use them on the new P-TTL bodies though
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