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07-11-2017, 06:48 AM   #1
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How to workaround Pentax MX flash-sync limit? HSS or similar?

I'd like to use a flashgun with my Pentax MX but I know the sync speed limit is 1/60, which is disappointing.
I'm wondering if there is a way of using higher shutter speeds with something like HSS or an FP mode?

I'm new to flash and it's my understanding that modern HSS is a feature of the camera and not the flash (?)
Failing everything else, I'd be interested to hear of alternative workflows, possibly with continuous lighting.

Very interested in reading your thoughts on it!

07-11-2017, 07:27 AM - 1 Like   #2
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That is why I got an ME Super with my MX as it synchs at 1/125th -- still not as fast as the Nikon FE 2 at 1/250th -- when I was doing local Press Photography I ran out of apertures in bright light with 200ASA film loaded if I wanted to use Fill-in flash but my competitors with 1/250th could still keep going ! You cannot use any higher than 1/60th on the MX -- HSS works only with an 'electronic shutter' not the 'clockwork one' of the MX . I have worn out the flash synch port on my MX ! Even my K10D only synchs up to 1/180th and you would think Pentax could have got 1/250th by now -- my 'Professional' LX only synchs up to 1/75th == worse still for a 'Professional' camera.
07-11-2017, 08:16 AM   #3
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QuoteOriginally posted by pentaxpete Quote
That is why I got an ME Super with my MX as it synchs at 1/125th -- still not as fast as the Nikon FE 2 at 1/250th -- when I was doing local Press Photography I ran out of apertures in bright light with 200ASA film loaded if I wanted to use Fill-in flash but my competitors with 1/250th could still keep going ! You cannot use any higher than 1/60th on the MX -- HSS works only with an 'electronic shutter' not the 'clockwork one' of the MX . I have worn out the flash synch port on my MX ! Even my K10D only synchs up to 1/180th and you would think Pentax could have got 1/250th by now -- my 'Professional' LX only synchs up to 1/75th == worse still for a 'Professional' camera.
Ah! I had no idea the ME Super was faster! I only got my MX recently (first film camera) mainly based on the reviews here but I didn't really pay attention to sync speed at the time. I suspected HSS was a modern feature, but I stumbled upon "Focal Plane Flashguns" mentioned here, which may be useful. I have seen FP modes mentioned on flashgun specs but I'm not sure if it's all electronic or if it would work like similarly to the ones mentioned in the link? I know there is an FP socket on the MX...

Last edited by cloudbusting; 07-11-2017 at 08:23 AM.
07-11-2017, 09:39 AM - 1 Like   #4
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Insofar as I know, nobody makes FP flashbulbs any more and the FP port is essentially obsolete. The FP bulb would burn at peak output for the entire time it took both curtains to traverse the shutter plane and the release of the curtains was timed appropriately, so sync at any speed up to the MX's 1/1000 was possible, but I don't think the current run of HSS electronic flashes can do this and high-speed sync on DSLRs demands that the camera and the flash are talking to each other (which the MX can't).

I have recently read about "hypersync" flash, which does mimic the extended discharge of the old flashbulbs, but it seems to be a specialised thing. I don't know of any camera-mounted units that do it or whether their burst duration and intensity vs time profile would match in timing to the FP port on a manual camera.

07-11-2017, 10:11 AM   #5
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QuoteOriginally posted by pathdoc Quote
Insofar as I know, nobody makes FP flashbulbs any more and the FP port is essentially obsolete. The FP bulb would burn at peak output for the entire time it took both curtains to traverse the shutter plane and the release of the curtains was timed appropriately, so sync at any speed up to the MX's 1/1000 was possible, but I don't think the current run of HSS electronic flashes can do this and high-speed sync on DSLRs demands that the camera and the flash are talking to each other (which the MX can't).

I have recently read about "hypersync" flash, which does mimic the extended discharge of the old flashbulbs, but it seems to be a specialised thing. I don't know of any camera-mounted units that do it or whether their burst duration and intensity vs time profile would match in timing to the FP port on a manual camera.
Thanks pathdoc for your helpful reply. Yeah, I came across "hypersync" on my internet travels. At least it's something to bear in mind as far as digital shooting goes. I guess my MX will inspire some manipulation of available light with a reflector or two at least! I''m looking to buy a medium format film camera to play around with so I'll definitely bear flash sync in mind for that. I believe copal leaf shutters are the way to go from what I read
07-11-2017, 10:35 AM - 1 Like   #6
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Maybe! But tricky!

HSS requires specific features in BOTH the flash and the camera. The flash needs a special circuit to run the flash bulb at lower power for a long duration rather than a single flush pulse (which standard flash does). And the camera needs a different flash trigger circuit to fire the HSS flash BEFORE the first curtain opens rather than after the first curtain opens (which is required for standard flash).

Now what is interesting is that old style FP flashes are somewhat similar to HSS both in putting out a long duration of light and needing a camera trigger that fires BEFORE the curtain opens. That's the good news. The maybe tricky part is that FP requires the trigger 1/60 of second before the curtain opens to give the flash bulb time to start burning and reach a steady burn rate. In contrast HSS probably expects the trigger only an instant before the first curtain opens. Fire an HSS flash with the FP trigger on the MX and the flash will be firing for 1/60 of second before the curtain even opens and wasting all that light. And depending on the full flash duration of the HSS flash, it will probably be done firing before the MX curtain closes and may even be done for it's even started. (It depends on the flash sync time of the camera that the HSS is programmed to work with).

Getting it to work seems to require getting the HSS flash to fire for longer (if it fires for about 1/20 to 1/24 of second, that should fully illuminate the frame at a shutter time of 1/125 or faster) but if you (or someone you know) can build a little delay circuit to convert the MX's FP trigger timing to something more like HSS, then less of the HSS light would be wasted and you wouldn't need as long an HSS duration.

Good luck!
07-11-2017, 11:15 AM   #7
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QuoteOriginally posted by photoptimist Quote
Fire an HSS flash with the FP trigger on the MX and the flash will be firing for 1/60 of second before the curtain even opens and wasting all that light. And depending on the full flash duration of the HSS flash, it will probably be done firing before the MX curtain closes and may even be done for it's even started. (It depends on the flash sync time of the camera that the HSS is programmed to work with).
That's presuming the flash will even fire in HSS mode on a non-compatible camera. HSS generally works by firing in pulses; as the open slit between front and rear curtains crosses the field of view, in such a way that the entire FOV is "painted" in non-overlapping fashion as the slit moves across. This is why it is short-ranged; the capacitors can't recharge in time before the next burst is demanded to yield full power. That's also why it needs to talk to the camera, to determine the exact interval at which to fire (determined by the width of the slit, which in turn is determined by the selected shutter speed).

I have on one occasion plugged an electronic flash on single-discharge mode into the FP port of a manual camera and fired it deliberately at a subject which was well within illumination range. The result was a gross under-exposure which appeared to be uniform across the frame. This suggests that with electronic flash on FP timing, a single discharge at least is all over and done with before the first curtain starts to move. Firing in HSS mode, even if it can be forced, is probably going to produce the same result.
07-11-2017, 11:45 AM   #8
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QuoteOriginally posted by photoptimist Quote
Maybe! But tricky!

HSS requires specific features in BOTH the flash and the camera. The flash needs a special circuit to run the flash bulb at lower power for a long duration rather than a single flush pulse (which standard flash does). And the camera needs a different flash trigger circuit to fire the HSS flash BEFORE the first curtain opens rather than after the first curtain opens (which is required for standard flash).

Now what is interesting is that old style FP flashes are somewhat similar to HSS both in putting out a long duration of light and needing a camera trigger that fires BEFORE the curtain opens. That's the good news. The maybe tricky part is that FP requires the trigger 1/60 of second before the curtain opens to give the flash bulb time to start burning and reach a steady burn rate. In contrast HSS probably expects the trigger only an instant before the first curtain opens. Fire an HSS flash with the FP trigger on the MX and the flash will be firing for 1/60 of second before the curtain even opens and wasting all that light. And depending on the full flash duration of the HSS flash, it will probably be done firing before the MX curtain closes and may even be done for it's even started. (It depends on the flash sync time of the camera that the HSS is programmed to work with).

Getting it to work seems to require getting the HSS flash to fire for longer (if it fires for about 1/20 to 1/24 of second, that should fully illuminate the frame at a shutter time of 1/125 or faster) but if you (or someone you know) can build a little delay circuit to convert the MX's FP trigger timing to something more like HSS, then less of the HSS light would be wasted and you wouldn't need as long an HSS duration.

Good luck!
Hi photoptimist. Indeed I thought the similarities between the old and new systems were interesting enough to yield some possibilities but it seems tricky alright. I was thinking of a very roundabout solution that would probably be too impractical for serious use, however! -

If it was possible to trigger the camera shutter at a chosen time after triggering the flash (something like an intervalometer, but with the flash triggered first) , with a bit of experimentation, do you think a HSS flashgun could be used in this way? Even if such a thing could even be done, it would only be useful in studio in limited (desperate?!) circumstances - but it's just a thought!

07-12-2017, 03:41 AM   #9
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OP, the ultimate question is why you need a higher sync speed. If it's to kill ambient light to allow a wider aperture for narrow DOF, perhaps what you need to do is use ND filters to let you open up, then increase the flash power.

Otherwise you are stuck with the limitations of your system, which - let's face it - weren't limitations when the MX was new on the market; you just bought FP bulbs for the times you needed them and shot at whatever speed you desired. There was no NEED for a higher X-sync speed. Remember; the ME was the real ground-breaker (full-time Av, metal shutter); the MX was that system workhorse that had to be reliable and dependable as well as break ground in smallness, so they probably wanted to be more conservative with that design and stick with the cloth shutter they were familiar with and knew how to make work.
07-12-2017, 05:34 AM   #10
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QuoteOriginally posted by pathdoc Quote
Remember; the ME was the real ground-breaker (full-time Av, metal shutter); the MX was that system workhorse that had to be reliable and dependable as well as break ground in smallness, so they probably wanted to be more conservative with that design and stick with the cloth shutter they were familiar with and knew how to make work.
The main advantage of the cloth shutter is that it works without any batteries...
07-12-2017, 05:40 AM - 1 Like   #11
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QuoteOriginally posted by cloudbusting Quote
Hi photoptimist. Indeed I thought the similarities between the old and new systems were interesting enough to yield some possibilities but it seems tricky alright. I was thinking of a very roundabout solution that would probably be too impractical for serious use, however! -

If it was possible to trigger the camera shutter at a chosen time after triggering the flash (something like an intervalometer, but with the flash triggered first) , with a bit of experimentation, do you think a HSS flashgun could be used in this way? Even if such a thing could even be done, it would only be useful in studio in limited (desperate?!) circumstances - but it's just a thought!
There's two trigger hacks possible: 1) trigger the HSS flash gun and then trip the camera's shutter; 2) trip the camera's shutter and use a delay circuit on the FP flash sync port to trigger the HSS flash. Both can work with the best results coming from which ever has the most predictable/reliable timing. I'd think #1 would be hard because it relies on knowing the EXACT time delay between hitting the shutter button, the mirror lifting, and the first curtain starting to open. Variations in temperature, lubrication, and wear probably make the shutter-button-to-curtain-opening pretty unpredictable. In contrast, the FP sync-to-curtain opening should be more stable which makes option #2 more reliable. Option #2 has the advantage of being less obtrusive -- just a little box on the cord going to the FP flash sync port -- instead of some mechanical contraption mounted on top of the camera's shutter button.

In any case, pathdoc is right about a second layer of trickery being required. Modern-day HSS flashes need to be told by the camera exactly what to do. There's little strings of digital data, synchronization clocks, etc. going back and forth between the flash and camera. The two devices talk to each other about power settings, aperture, shutter speed, flash mode, flash readiness, triggers, etc. It's a little conversation between camera and flash and unless the camera says the right things, the flash won't do anything. Obviously the MX does not speak the language of any modern flash. But it's exactly the sort of thing a properly programmed Arduino microcontroller (and dedicated electronics/software hobbyist) can readily do and maybe someone out there on the internet has already done.
07-12-2017, 07:47 AM   #12
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QuoteOriginally posted by boriscleto Quote
The main advantage of the cloth shutter is that it works without any batteries...
I'm pretty sure my battery-independent-except-for-the-meter XR-1 has a metallic shutter. The decider AFAIK is whether it's electronically controlled, not what the curtain construction is. Even then, regardless of curtain construction, there is variation in how much manual reversion you have. ME? Drop a 100 ASA film in and you are on Sunny 16. LX? Any hand-held speed with a normal lens is there for you. Super Program? Forget about it.
07-12-2017, 07:58 AM   #13
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QuoteOriginally posted by pathdoc Quote
I'm pretty sure my battery-independent-except-for-the-meter XR-1 has a metallic shutter.
And the electronic Spotmatic ES has a cloth shutter...
07-12-2017, 10:55 AM - 1 Like   #14
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You could get a camera with leaf shutters.
For example the RB67 has a wide range of lenses in leaf shutters.

Big and heavy though, compared to MX.
https://app.box.com/s/o9rcry86192yykanz7ruy24v52rj3qwd
07-22-2017, 12:33 PM   #15
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QuoteOriginally posted by pathdoc Quote
OP, the ultimate question is why you need a higher sync speed. If it's to kill ambient light to allow a wider aperture for narrow DOF, perhaps what you need to do is use ND filters to let you open up, then increase the flash power.

Otherwise you are stuck with the limitations of your system, which - let's face it - weren't limitations when the MX was new on the market; you just bought FP bulbs for the times you needed them and shot at whatever speed you desired. There was no NEED for a higher X-sync speed. Remember; the ME was the real ground-breaker (full-time Av, metal shutter); the MX was that system workhorse that had to be reliable and dependable as well as break ground in smallness, so they probably wanted to be more conservative with that design and stick with the cloth shutter they were familiar with and knew how to make work.
I guess the main reason I'd want faster flash is to freeze motion, particularly with portraits where sharp features, eye reflections etc are important. @photoptimist An arduino project sounds interesting. I may have a look around to see if it's been done.

@wombat2go Since this post I actually ended up buying a Bronica SQA I got a beat up body on ebay for 50 quid so I'm hoping to assemble different backs, finders etc over time.
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