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11-18-2012, 02:29 AM   #1
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Home-made wireless P-TTL triggers?

Hi all,
I know wireless triggers have been discussed here on the forum before, but I haven't found exactly what I'm looking for.
Although I've had basically zero experience with wireless flash so far, I've been thinking and reading about it and it bothers me that there are virtually no wireless P-TTL flash triggers available for Pentax at the moment (ok, there are those Aokatec ones - but how long will the camera battery last if you fire a flash every time?) So I was thinking: would it be so difficult to modify p-ttl triggers designed for other brands? And if modified, do you think they would actually work? Like, there are i-ttl triggers for Nikon, for example. The pin layout looks VERY similar to Pentax flashes, but ok, there must be small differences and the pins of a Pentax flash probably wouldn't touch the pins on a Nikon receiver. BUT, what if I took a transmitter and receiver for Nikon and changed the hot-shoe for a Pentax one? Re-soldered it? Do you think it might work? Is there any special Pentax 'protocol', any sequence of signals, that might prevent this from working? My thinking is, if the number of pins is the same, what the heck does it matter what sequence of signals Nikon or Pentax uses? All that the transmitter does is send signals, and all that the receiver does is receive signals, right? So if I could achieve correct contact between the hot-shoe and the camera/flash, it should work, shouldn't it?
English is not my mother tongue, but I did my best to make myself clear and hope you understand what I mean Your opinions are appreciated, thanks in advance.

11-18-2012, 06:42 AM   #2
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I don't know what the issue with pTTL and wireless triggers is. It could be a licensing issue (such as can't claim to be pTTL) or an engineering one (special chip). In either case I don't believe if it were a simple procedure that we wouldn't see them on fleabay. I mean they go to the trouble to make and sell other Pentax compatible knockoff stuff on there, so if a rewire or different hot-shoe on one of their cheap triggers should have shown up by now. Have a go at it if you believe otherwise.
11-18-2012, 05:53 PM   #3
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I have read that the P-TLL signal that is sent out by is proprietary to Pentax .... it isn't JUST a flash of light. 3rd party flash manufacturers have to reverse engineer the data contained in the pre-flash. Some manufacturers achieve better success than others.

If you would be satisfied with a pseudo P-TTL solution, pair the Seagul SYK-5 optical sensor with an auto-thiristor type flash-
https://www.pentaxforums.com/forums/pentax-flashes-lighting-technique/185932-...pttl-sort.html
11-18-2012, 07:06 PM   #4
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What the aokatec tries to do is just an IR to RF (and back to IR) "bridge" between the on camera and the off camera flash.

Since Happyman doesn't want to fire the on camera flash to get the IR bridge to work...the only other option is to use the data on the hotshoe.

I assume that the camera only transmits and the flash only receives (which might or might not be the case). If the flow of data is unilateral, it should be fairly easy. Now, the only obstacle is to know what type of signals actually go out of those 5 pins of Pentax (one of them is presumably ground, so that leaves us 4 signal to decode).

11-18-2012, 09:17 PM   #5
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Very creative thinking, but....
QuoteOriginally posted by Happyman Quote
would it be so difficult to modify p-ttl triggers designed for other brands?
Yes.

Metz and Sigma, the only two companies making Pentax p-TTL compatible flashes, many times having problems reverse-engineering the protocol used by Pentax.
QuoteOriginally posted by Happyman Quote
And if modified, do you think they would actually work?
Call me a non-believer, but I don't think so.
QuoteOriginally posted by Happyman Quote
Is there any special Pentax 'protocol', any sequence of signals, that might prevent this from working?
Definitely. That's why it's called "proprietary."
QuoteOriginally posted by Happyman Quote
All that the transmitter does is send signals, and all that the receiver does is receive signals, right?
That's right.
QuoteOriginally posted by Happyman Quote
So if I could achieve correct contact between the hot-shoe and the camera/flash, it should work, shouldn't it?
Uhm.... My boss and I use the same set of telephone. When he talks to his wife in Dutch, I have no clue as what they are talking about. When I talk to my wife in Vietnamese, he in turn has no clue.

I wouldn't try to talk to my boss in Vietnamese, have him translate to Dutch and relay to his wife, then have his wife translate back to Vietnamese and relay to my wife.

Last edited by SOldBear; 11-18-2012 at 09:26 PM.
11-21-2012, 05:40 AM   #6
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Original Poster
Ok, guys, thanks for all your input. I've also asked on an English and Slovakian forums and now I'm pretty much convinced that the best thing (or the only thing) to do is either wait for some manufacturer to make P-TTL transmitters or buy Cactus V5s and stick to manual mode. And I'm OK with that, I suspected in the very beginning that my solution wouldn't quite work, I just wanted to hear other opinions, so that I quench my thirst for this kind of info and sleep well
Cheers,
Juraj
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