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06-09-2010, 04:27 PM   #1
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Has Anyone Had Luck Getting A Flash To Trigger Without HSS Above 1/180th

Just curious if anyone has been able to hack this one on any Pentax DSLR?

06-09-2010, 05:26 PM   #2
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With Pentax? Not possible ARGH!!!

For some reason, Pentax thinks all of their users are complete idiots and would have no use for using flash higher than the sync rate. (this would cause the shutter to be only partially open during the flash and cause a dark band to appear)
So the hot shoe and the sync socket are both disabled at shutter speeds higher than the max sync speed.
Very frustrating when you "KNOW" how the camera and lighting work together and you wish to use that to your advantage. Yes, that dark banding *can* be used for good, if you know what you're doing.

Sadly Pentax "knows better".

I suppose if you're an electronics wizard, you could try to do some sort of hack using a HS flash to trigger another external flash. But that would require some electronics work well beyond my ability, in order to fire the "slave" at the right time.
06-09-2010, 05:47 PM   #3
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Well my thought would be to just make the camera think its connected to a flash with HSS.

Perhaps an AF360/540 with a broken flash could be modified for such a purpose?
06-09-2010, 05:55 PM   #4
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High Speed Sync you can...
"Regular use" flash = no
After tons of questions I have figure it out... after tons of answers

On the AF-360 I don't know on the 540 or others moves the lever all the way to the right... turn to manual mode on the camera and shoot... of course keep on turning up your shutter speed.

However I think the question is not can you HSS, but can you do it wirelessly?

06-09-2010, 06:37 PM   #5
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QuoteOriginally posted by C.W Tsorotes Quote
Well my thought would be to just make the camera think its connected to a flash with HSS.
Perhaps an AF360/540 with a broken flash could be modified for such a purpose?
Yeah, you would need to somehow tap in after the pre-flash and then sync with one of the illumination flashes. You would not want to catch any metering or communication flashes and would need to wait or somehow determine when the first actual flash is started that is supposed to be seen by the sensor.

If you can cripple the 360/540 in some way or rig up something to catch the right signals, then you have something workable. You do need some sort of brains in the system that will talk to the camera and fool it somehow. Your idea of a broken PTTL flash is probably a good start. :-)

Wish I knew enough electronics. The concept actually seems simple enough. The HS flashes would be so minuscule that you would not even need to disable the PTTL flash after the first signal is caught... assuming you're signaling an external strobe of sufficient power.
06-10-2010, 01:48 PM   #6
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One thing that does not work is to put the PTTL flash on the hot shoe in HS mode and connect the PCSync cable. The PC Sync (perhaps the center pin on the whole) is still disabled when shutter speed is above the max sync speed.

Just cannot catch an easy break, eh?

I cannot even find the hotshoe wiring diagrams any more. It would seem at the very crudest that you should be able to count pulses off one of the darned pins and actuate an external flash at the correct time that way. (It should be a simple circuit, but its been 20 years since I've done that stuff. Radio Shack doesn't even carry those simple electronics any more.).
06-11-2010, 01:45 AM   #7
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cant sync above 1/180s without HSS flash

Here's the reason. The shutter consists of two curtains - one opens across the sensor, then the other follows and closes across the sensor.

The Pentax system can expose the whole sensor this way up to 1/180 sec. At higher speeds, the second curtain starts to move before the first curtain reaches the opposite side of the sensor area. The sensor is then exposed by a strip of light moving across the sensor.

If a normal flash fires at any shutter speed above 1/180sec, then only a strip of the image will be illuminated and the rest will be dark.

HSS flashes send out very fast pulses of light, effectively retaining illumination for the duration of the exposure.

In the old days of flash bulbs, the bulb would burn a lot longer than the shutter speed and high speed flash photography depended only on shutter speed. With electronic flash, the slowest duration of flash is about 1/2000s.

Hacking the camera is not an answer, one has to hack a flash unit to get it to stream out a sequence of pulses of light - assume that the slowest flash duration is 1/2000, then you need to get it to stream out 12 such flashes in 1/180sec. Each flash pulse should only use a maximum of 1/12th the available power or else the flash will run out of power before the final pulse is transmitted.
06-11-2010, 02:18 AM   #8
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Exactly.
But I do not want to create a high speed flash, we've got plenty of those.
I simply want to use a standard flash with the camera at higher shutter speeds.
The shutter curtain behavior can be used to creative extent, and should not be a reason for disabling the flash completely.

At least that is my intent. Not sure about C.W Tsorotes. (But I believe we both wanted the same ability)

I simply want to get the signal for the first illumination flash and signal off that.
The simplest method would be to hack a flash to get that signal.
Now, of the firmware hackers could re-write the Pentax firmware, perhaps then we'd have an in-camera solution. (probably not going to happen. :-) )

06-11-2010, 05:33 AM   #9
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I think you need to explain exactly why you want the flash to fire above 1/180. exactly what effect do you want?

Note that you have 2 possibilities, leading curtain sync and trailing curtain sync.

With leading crutain sync the flash will fire when the leading curtain reaches the end of travel (if I recall correctly it moves upwards). If you fire the flash at this point, you will have the top portion of the sensor exposed, with a fuzzy edge at the bottom, fading from dark to exposed which will be a function of the flash duration and the speed of the trailing curtain.

With trailing crutain sync you will have the flash fire as the trailing curtain leaves the bottom, on its upward travel, having a fuzzy band from the bottom upwards as a function of the speed of the curtain, and a similar fuzzy band at the top again as a function of the speed of the leading curtain and the duration of the flash. the width of the correctly exposed portion of this band, IF ANY will be a function of the shutter speed selected, and the width of the "slit" made by the two curtains to achieve the effective shutter speed.

I see nothing artistic or creative about an exposed band on the sensor, unless you think that you can blend this with natural lighting to have a darker image except for one zone, but again, I can't see how that would be creative.
06-11-2010, 06:42 AM   #10
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QuoteOriginally posted by Lowell Goudge Quote
I see nothing artistic or creative about an exposed band on the sensor, unless you think that you can blend this with natural lighting to have a darker image except for one zone, but again, I can't see how that would be creative.
If you are shooting outdoors and there is enough ambient light, then you can use the flash on your subject, and the area that doesn't get flash exposure is still exposed properly by the ambient light.
06-11-2010, 06:53 AM   #11
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QuoteOriginally posted by alohadave Quote
If you are shooting outdoors and there is enough ambient light, then you can use the flash on your subject, and the area that doesn't get flash exposure is still exposed properly by the ambient light.
I understand that, but the point is that that is the purpose of HSS, or fill flash below the sync speed.

this thread wants to use regular flash, above sync, and expose only a horizontal band the width of the shutter opening, with the flash. I see nothing artistic about this.
06-11-2010, 08:53 AM   #12
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It's not going to be usefull at much higher speeds, but if you need fill flash only for half the frame, you should be able to sync at 1/360, or in practice at least 1/250, if the camera would just fire the flash.

There is at least one person doing this to good effect with Canon, I see no reason to forbid it on Pentax just because not everyone wants to use it. Especially with radio triggers, when you just can't use HSS (as far as I know anyway, though I see no real reason for it).

Digital ProTalk: Technique Tuesday: My Cheatin' Light - Or How To get Your Flash To Sync At Higher Sync Speeds Than Normal, and Alligators On Location
06-11-2010, 09:53 AM   #13
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In looking at these effects, all of them could be achieved simply with a snooted flash or a lower flash sync, and flash because all of the areas behind the image would be illuminated any way with natural lighting and the flash is offering at best about 1/3 stop of additional lighting to make the bride and groom "pop.

while the technique might offer some benefit, there are other ways to achieve it, and it was probably initially thought of / discovered by accident.

I personally don't see much point in it, but, if you want to try this type of thing, why not design a small sound activated or electrically activated flash trigger with built in delay to fire the flash when you want. Note, on the camera, although there are a lot of variables, I am willing to bet that the time lag from triggering the shutter to leading curtain travelled fully is one of the most tightly controlled. As a result, using a separate trigger button on a bracket, triggering the shutter and a delayed trigger on the flash would do the trick
06-11-2010, 01:28 PM   #14
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Why?
When shooting above the sync speed the curtain starts to come into frame and becomes a built in ND Grad (closest description of the effect).
You can use this to properly expose an overly bright sky, or to bring down the exposure on a bride's dress to match the rest of the scene. (to use two over-popularized examples)

The weak HSS flash cannot overcome the ambient light beyond VERY short distances compared to what a non-HSS flash can do. (Unless perhaps you are Joel McNally and can have 16 HSS flashes)
The alternative is to bring in overly expensive and heavy strobes, extension cords, batteries, etc... to overcome the ambient light and then bring down all of the light with aperture and ND filters.
A little higher shutter speed when used with the non-HSS flash can help lot.

The plain fact of the matter is that Pentax cripples their equipment and some people are looking for a way to make this work -- without switching to other brands of equipment that do not coddle and babysit their users into pure textbook approaches to photography.


Sound activated triggers, while perhaps a good idea for timing the shutter, work best while the shutter is held open in bulb mode. Cannot really make this work well in daylight situations. The issue is to get faster shutter speeds, not slower ones. Dunno what would be needed to time the sound with the shutter without either cracking into the camera or the flash, at which point sound activation would be unnecessary anyway.
06-11-2010, 01:36 PM   #15
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QuoteQuote:
this thread wants to use regular flash, above sync, and expose only a horizontal band the width of the shutter opening, with the flash. I see nothing artistic about this.
Thats sad.
What do you consider artistic? (no need to answer) I just hope you do not believe all photography has to follow instructions from a classroom or a book.
Either way, your choice.

I don't want to get into an argument of semantics or of what is/isn't creative.
I would just like to make the kind (and hopefully respectful) suggestion that you open your mind to other ideas. You may not like them, but at least it might give you other ideas that are to your liking.
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