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08-13-2009, 02:26 PM   #1
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Test: K20D PC sync and older flash

One of the advantages of K20D over it's predecessor K10D is PC sync plug placed on the left side of the camera. With announcement of K20D the plug was advertised as suitable for "external" flashes. And so a hype among Pentax users began and everyone wanted to know if PC sync was safe to use with high trigger voltage flashes. Unfortunately Pentax didn't provide a definite answer (or is it just google that can't find it?). Various posters on forums had their own opinions and educated guesses, yet no one seemed to have any first hand experience to pass on. Is it safe to use flashes with hundred or more volts trigger voltage or not? Last evening I was yet again searching for the answer, yet again of no avail.
This time I had enough of it and decided to test it on my camera. I plugged Vivitar 283 with measured trigger voltage of 109V on K20D PC sync. I switched on the flash, switched on the camera and reluctantly pressed shutter button. The flash of course fired, but will it fire again? I pressed again and flash fired. I continued firing, made about 25 exposures and PC sync plug was still working. Today I fired a couple more exposures and everything still works as it should. Given the test I made I'm quite positive that PC sync plug isn't there only to spare you a PC/hot-shoe adapter, but is also high voltage protected. It's nice to know that instead of über expensive Wein safe sync I can use a cheap hot shoe adapter with PC cable. Mind that bottom of adapter is plastic and there is no contact between flash and camera hot shoe.


08-13-2009, 05:23 PM   #2
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Yep according to JohnCPentax it is high voltage protected. Go to uTube do a search on the K20D and watch the video with John Carlson talking about the K20D, he makes mention of the fact. How did you know for sure? There are flashes with higher voltages isn't there? For example my old Kodak P880 was rated for use with triggers up to 500volts, this per one of Kodaks engineers.
08-13-2009, 05:37 PM   #3
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Based on Matjazz's experiment, trigger voltage as high as 109V does not have any immediate effect on the K20D.

But it doesn't say what the high limit is. I have a Vivitar 283 with 184V, and a Metz 45 CT-1 with 224V trigger voltage. I don't know what they will do to a K20 (not that I have one).

Also, no one can tell what the long term effect is. The camera body may be OK after 100 flash exposures, but may not work after 110 exposures.

I don't doubt your result, Matjazz. What I'm trying to say is that there is still not enough data. After all, no one has reported a K20D being damaged by high trigger voltage.
08-13-2009, 06:31 PM   #4
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I've shot several thousands of exposures using either a Metz 60 CT-2 and a Norman P2000D, using the PC socket for both. I don't know what the trigger voltage is on either of them, but they are both very old school flash units that predate the era of fiddly electronics in cameras.
The Norman will, from time to time, forget to reset it's trigger and run straight from power supply to the flash tubes.
I have yet to have a camera failure.
For all of Pentax's many faults, I really doubt that they would put a PC socket onto a camera and not have voltage protection built into it. It's one of those things that you release into the wild and have no control over, so you had better do it right.
I suspect that no one has reported a camera failure because a camera failure of this type is not going to happen.

08-14-2009, 12:49 AM   #5
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QuoteOriginally posted by SOldBear Quote
Based on Matjazz's experiment, trigger voltage as high as 109V does not have any immediate effect on the K20D.
But it doesn't say what the high limit is. I have a Vivitar 283 with 184V, and a Metz 45 CT-1 with 224V trigger voltage. I don't know what they will do to a K20 (not that I have one).
Also, no one can tell what the long term effect is. The camera body may be OK after 100 flash exposures, but may not work after 110 exposures.
I'm aware that damage might catch up later on, but to me a PC sync that can't be used with older flashes is as good as a fried one.

QuoteOriginally posted by Wheatfield Quote
I've shot several thousands of exposures using either a Metz 60 CT-2 and a Norman P2000D, using the PC socket for both.
The trigger voltage for those is 23-30V and 45V respectively. At least that's what they say on Photo Strobe Trigger Voltages. I have 60 CT-1 and have measured 29V.
08-14-2009, 05:07 AM   #6
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the manual pentax cameras are safe up to about 600 volts. Cannot cite the source of my information, but there are websites that quote that the maximum a Pentax Dslr can reliably and safely handle is 15V. The trigger voltage for the AF540FGZ is 5.8 volts but bear in mind the hot shoe voltage is often substantially less than what the PC synch socket can handle,The PC sync socket on most modern cameras can handle 100 volts and over, so I really wouldn't concern myself about it too much.

Last edited by Digitalis; 08-14-2009 at 05:14 AM.
08-14-2009, 09:54 AM   #7
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I've done some digging around on other cameras. Canon 20D has a PC sync that is safe up to 250V. Nikon D70 can take 250V even on hot shoe. Same goes for it's successors (D80, D90). It's all written in manuals:


I'm disappointed to see that Pentax hasn't put out any information regarding flash voltages. A camera that can cope with rain, snow and -10°C can get it's hot shoe fried by a feeble old flash

Last edited by Matjazz; 08-14-2009 at 10:11 AM.
08-14-2009, 05:55 PM   #8
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I've taken apart a few Pentax dSLRs, but not the K20d so I don't know for sure. I've also made my own flash triggers with solar panels from $1 solar calculators and 600v triacs. The triacs only cost a few cents and I would have to think that Pentax wouldn't spare that in the build for protection.

08-15-2009, 02:00 AM   #9
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QuoteOriginally posted by Matjazz Quote
I'm disappointed to see that Pentax hasn't put out any information regarding flash voltages. A camera that can cope with rain, snow and -10°C can get it's hot shoe fried by a feeble old flash
some "feeble old flashes" can chuck around as much as 500 volts. Pentax isn't exactly well known for making use of every marketing opportunity. Nikon market every single feature that sets their product apart from the competition wether or not the feature is even going to make a difference in 95% of photographs. Nikon made a huge deal in the mid 1990's about lenses that could transimit distance data back to the camera to improve accuracy with flash exposure. The funny thing is that a lot of Pentax lenses could do that even before Nikon made this big, monumental improvement...but pentax didn't advertise it...it's little more than a footnote in the camera manual. Don't sell pentax short, there is plenty of information availible about things like this on the internet if you look hard enough.

Last edited by Digitalis; 08-15-2009 at 02:11 AM.
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