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07-01-2007, 08:36 AM   #1
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I need a high speed flash, any thoughts?

After using the search option, I've decided to just post my own thread. Sorry if this has been asked a million times. I need a high speed sync flash, something that will work at a shutter speed of at least 1/500. What are the differences between the 360 and 540? Is the Sigma 500 an option? Thanks in advance.

07-01-2007, 09:01 AM   #2
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AFAIK all these flashes can only work synced up until 1/180 for SS, but please correct me if I'm wrong.

Also, the 540 does have swivvel while the 360 has not. The Sigma 500 has swivel and is far cheaper but reportedly has a crooked battery door.

Reports of inconsistant flashes in P-TTL mode have been reported with every flash AFAIK (worse with the 500), but I'm not sure if that's an issue for you? Also, using omnibounce from StoFen should get the results better using P-TTL.

All this is just written from what I've read on the internet. I am looking to buy a flash myself, and am balanced slightly towards the 540. Any tips are appreciated tho!
07-01-2007, 09:46 AM   #3
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Why? Not a trick question! What is so magical about 1/500?

Both of the Pentax units will work in High Speed Sync mode: flash at any shutter speed. It's effectively a subset mode of manual and some table look-up is required. Flash ( and other ) Manuals can be found here.
07-01-2007, 11:42 AM   #4
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1/500 to freeze action.

07-01-2007, 11:48 AM   #5
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I need a high speed flash, any thoughts?

Both the 360 and 540 will work in the high speed sync mode with the K10D. However, the 360 has a very fragile battery door. Mine has broken on two occasions and Pentax wants over a hundred dollars US to repair it. Therefore, I would not recommend buying the 360. The 540 is the way to go in my opinion.
07-01-2007, 12:56 PM   #6
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QuoteOriginally posted by reknelb Quote
1/500 to freeze action.
I think you have a rather incomplete understanding of the nature of flash. On camera and hotshoe mounted external flash of the type mentioned have flash duration from approximately 1/20000 to 1/2000 second (or longer)--the longer time corresponding to greater/greatest light output. This light energy is distance limited. Syncing a flash as in x sync insures that the flash fires after the shutter is completely open, but before it closes--not really a big problem as the shutter is open much much longer than the flash burns.

The high speed sync I mentioned simply insures that the peak burn point is somewhere in the shutter open time-hence the need for a chart (which should be verified by experimentation as it (the chart) was derived from such experimentation in a laboratory; i.e. not real life).

Regardless of mode a proper setup would insure that light from a flash reaching a subject fairly close to the camera then reflecting back to the sensor is usually sufficient for stopping most ordinary things: human sports involving balls, bats, etc. There may be background blur, but that is typically outside the DoF range, so who cares.

If you have a specialized capture need: a bullet, water drops, etc, one typically works in the dark with a sound or motion trigger or a timer on the flash and bulb mode on the camera.

1/250 or 1/350 are typical fast end limits on shutter/flash sync. A more verbose description of your needs would facilitate the generation of pertinent answers.
07-01-2007, 01:36 PM   #7
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As I understand it, HSS is only needed when there is a requirement for a high shutter speed in addition to the motion-stopping capabilities of the flash itself. (i.e. getting rid of ambient light with a high shutter speed)

If you can live with the ambient exposure given by a shutter speed of 1/180 or lower, HSS is not needed - the flash duration is far lower, and as it is the primary source of light, the actual shutter speed doesn't matter.

HSS is for when a 1/180 shutter speed would result in a significant ambient exposure when you have a preference for flash as the primary light source. Any shutter speed faster than 1/180 will result in only part of the frame seeing the flash if the camera and flash don't support HSS, as the shutter is never fully open but essentially "travels" across the sensor. I believe HSS somehow fires multiple flashes such that the entire sensor can be covered despite the "traveling slit" behavior of the shutter.

So if you're trying to stop motion with the flash and overexposure of ambient isn't a problem, any flash will do.
07-01-2007, 01:38 PM   #8
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Got a sigma super 500, and been up to 1/1000 but i'm a noob in this flash business so except the fact that it works I can't help.

07-01-2007, 02:09 PM   #9
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Not a multiple flash. A controlled release of stored electricity to insure a longer maximum intensity burn time. And timing to insure this peak light output covers the time the shutter is open. Overall Maximum output is lowered to increase duration.
07-01-2007, 02:48 PM   #10
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I have to chime in here.

When using X sync at 1/180th of a second the effective shutter speed is the duration of the flash. In the case of my old manual SLR (I do not have a flash that is compatable with my Pentax digitals - and the built in flash is a joke) at 1/60 of a second x sync the flash duration was 1/2000 of a second. Therefore action was stopped.

Now back in the days of flash bulbs - they were designed to be burn at peak output for about 1/30 of a second. Therefore you could have high shutter speeds when using flash bulbs. With the focal plane shutters on Pentax digital cameras you have to have long flash durations to use high shutter speeds. The modern thyristor flashes use light reflected from the subject back to the flash unit, either through the camera or on a sensor on the flash to set the duration of the flash not the total brightness.

This is not going to be cheap. Sit down with at good instruction book on Guide numbers and flash - learn how to use flash the old school way. It will be "enlightening".

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07-01-2007, 03:12 PM   #11
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QuoteOriginally posted by jfdavis58 Quote
Not a multiple flash. A controlled release of stored electricity to insure a longer maximum intensity burn time. And timing to insure this peak light output covers the time the shutter is open. Overall Maximum output is lowered to increase duration.
Thanks for the clarification - I was wondering how the heck they pulled off multiple pulses perfectly synchronized so as not to cause some sort of banding across the frame.
07-02-2007, 05:07 AM   #12
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here's an excellent article explaining why HSS does not work for stopping motion.
HSS
07-02-2007, 07:12 AM   #13
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QuoteOriginally posted by roy Quote
here's an excellent article explaining why HSS does not work for stopping motion.
HSS
Nice article, thanks for posting it.
07-02-2007, 07:45 AM   #14
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QuoteOriginally posted by roy Quote
here's an excellent article explaining why HSS does not work for stopping motion.
HSS
Interesting article: gotta love the internet! Just goes to show that measurbators have existed for a looong time. A spinning wheel has been the source of more confusion for photographers than perhaps any other object.

And the mashing of physics is truely something to behold!

Just for a second-pun intended- think about the flash, especially the flash tube. A small low pressure environment dominated by a single exotic gas; two electrode-one on each end; a trigger wire wrapped around the middle. As a large external capacitor is charged by a DC to AC inverter, a electrical potential develops across the tube from one electrode to another. Electrons in the outer shell of the gas become excited and jump to a larger orbital shell. They will largely remain there until the electrical potential is removed.

At the moment of firing a kick of electricity un-balances the gas equilibrium in the tube and a small nuclear reaction takes place: some of the electrons try to jump to another further out orbital shell but fail-too much energy required .They fall back to the original orbit) the ground state and in falling generate a photon ---light! The electron will try to climb out to the higher orbital shell as long as the electrical potential exists--as long as the capacitor has charge. Each time a photon is release the chain reaction can continue because this also serves as the kick to start another electron into the falling/photon release part of the cycle.

While there is great turbulence in the tube, a large magnetic effect and even a small crack like lightening produces, the reaction is effectively continuous but short lived--there is no strobing. Key features are the exceptional brightness of the photonic discharge and it's extreme color temperature purity. Another is that it can be repeated almost endlessly, as long as you have power to charge the system-with that same light quality. And finally, because the electrical circuitry operates near the speed of light and the electrons are pre-positioned to fall in their orbits with the subsequent release of photons, the flash 'begins' nearly instantaneously-remember it's really a short lived nuclear burn. With no discernable lowering of output or shift in color temperature.

Through circuitry we can control how much charge is allowed to flow. A sufficient but small flow produces the same intensity and color purity as a sufficient and longer flow, but for a shorter duration (1/20000 second) . The sufficient and longer flow (ex: a full power pop) produces the same reaction, the same light and light quality, but for a longer duration (1/2000 second or longer). HSS takes advantage of this longer flow characteristic.

The OP is correct in his assessment that a faster shutter speed will stop action. He misses the point that a flash can do the same task across a range of shutter speeds. The author of the article has been duped by his own faulty physics.

Choosing shutter speed or flash, or some other motion arresting scheme depends mostly on what action is being captured. Again, I repeat the request for more information as to the OPs intended subject.
07-02-2007, 01:11 PM   #15
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OK, I have to admit, I'm not a big fan of flash photography. I think the shots look terrible. I usually bounce whenever possible, or diffuse. I realize that a flash will help stop action, I just didnt realize how much it would help. I'm was looking for a hss flash to shoot indoor arena horse show events. Usually 1/500 under normal conditions will freeze action, sometimes there will be a little blur in the hooves. So I figured a high speed sync flash do the trick. That was an interesting article but, the 1/250 pic with the flash still shows a little motion. I want crisp shots, and my flash only syncs up to 1/180. ???? So I went and shot some pics of the only running/trotting thing available to me right now, my poodle. Turns out, 1/180 with a flash freezes action pretty good. You learn something everyday. I'll post some of the shots after dinner. Thanks for all the info.

On another note, what would be the point of buying a hss flash if they are a non factor for action??

Last edited by reknelb; 07-02-2007 at 02:20 PM.
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