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09-14-2010, 03:16 PM   #1
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Is Flash Sync Speed limited by the body or flash?

as above.

09-14-2010, 03:21 PM   #2
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QuoteOriginally posted by Reportage Quote
as above.
it is principally limited by the body, more appropriately the shutter, and the speed the blades traverse the screen. the faster the blades, the longer the frame can remain fully open for the duration of the flash.

Flash duration will have some minor impact because it must, uner full power be finished before the curtains move, otherwise you will get uneven lighting of the frame, usually top or bottom edge darker than the rest depending on direction fo travel.

what is really limiting, is that trailing curtain synz is by necessity slower because it has to allow for full flash duration also. and in pentax that means 1/2 full sync speed
09-14-2010, 03:39 PM   #3
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thanks. i hope the K-5 supports 1/500s because i believe thats what i need right now.
09-14-2010, 03:42 PM   #4
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Just out of curiosity, for what purpose do you need 1/500s sync instead of HSS? Power? Reduction of focal-plane-shutter-distortion?

09-14-2010, 03:55 PM   #5
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daytime fill use actually. And being 1/500s, should be able to cycle the flash faster for the next shot not to mention that being faster, should be easier to freeze scenes.

currently i need to be very close and at low power to get the burst image pics that i need. I am thinking 1/500 at full power should do the job easier without having to be paparazzi-in-your-face kind of situation.
09-14-2010, 04:50 PM   #6
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I heard that the K-5 will support up to 1/250s sync with a firmware update to be released in 2011.

Adam
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09-14-2010, 05:49 PM   #7
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QuoteOriginally posted by Adam Quote
I heard that the K-5 will support up to 1/250s sync with a firmware update to be released in 2011.

If the shutter is mechanically capable of being fully open at 1/250 second, why wait until 2011? If the shutter is not capable, how could a firmware update help?
09-14-2010, 07:04 PM   #8
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The only flash sync that ever existed at 1/500 was a leaf shutter

As. For 1/250 sync with firmware upgrade I find this hard to believe. A bigger issue will be the flash itself which I think would need a shorter duration than the 540FGZ. Although I can't prove it I think my 500FTZ has a shorter diluration but then it was designed for the PZ1 and 1/250 sync

09-14-2010, 07:12 PM   #9
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QuoteOriginally posted by noblepa Quote
If the shutter is mechanically capable of being fully open at 1/250 second, why wait until 2011? If the shutter is not capable, how could a firmware update help?
Could be a question of making the flash fire at the right moment (no lag from the shutter curtains open fully to the flash fires). Just speculation - the K-5 is all rumors at this point!
09-14-2010, 07:14 PM   #10
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QuoteOriginally posted by Reportage Quote
daytime fill use actually. And being 1/500s, should be able to cycle the flash faster for the next shot not to mention that being faster, should be easier to freeze scenes.

currently i need to be very close and at low power to get the burst image pics that i need. I am thinking 1/500 at full power should do the job easier without having to be paparazzi-in-your-face kind of situation.
You can sync most PENTAX DSLR's at 1/500 sec and higher if you use an external flash with high-speed sync capability. In this mode the flash will send several bursts so as to cover the entire frame as the shutter opening travels across the sensor.
09-14-2010, 07:14 PM   #11
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The firmware update would be to support a new Pentax external flash which will be also able to sync up to 1/250s.

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09-14-2010, 08:43 PM   #12
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QuoteOriginally posted by Ole Quote
You can sync most PENTAX DSLR's at 1/500 sec and higher if you use an external flash with high-speed sync capability. In this mode the flash will send several bursts so as to cover the entire frame as the shutter opening travels across the sensor.
I believe he is saying with the HSS power loss, he must get close. This is complicated by the fact that he wants to bursts, as well.
09-15-2010, 11:26 AM   #13
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QuoteOriginally posted by Lowell Goudge Quote
Reportage

The only flash sync that ever existed at 1/500 was a leaf shutter

As. For 1/250 sync with firmware upgrade I find this hard to believe. A bigger issue will be the flash itself which I think would need a shorter duration than the 540FGZ. Although I can't prove it I think my 500FTZ has a shorter diluration but then it was designed for the PZ1 and 1/250 sync
According to the manual at PentaxImaging.com, the longest flash duration of the AF540FGZ is 1/1200 second, far less than 1/250 second. So, if the shutter were capable of being fully open at 1/250 second, the 540 should be able to sync to it.

I still don't see how a firmware update could help. If the shutter is not fully open at 1/250 second, no firmware update is likely to be able to change that. If it is fully open at 1/250, then any flash should be able to sync to it.

I don't claim that a new flash might not require a firmware update, but I don't think it will be because of sync speed.

HSS sync is really a different animal, altogether. It basically turns the flash into a continuous light source, by flashing multiple times during the exposure. Someone ran a series of tests on this forum, or another forum, a few months ago. He showed a table fan shot with a normal flash. The blades were completely frozen. With HSS, however, the blades were a complete blur, until he was able to get the shutter speed up over 1/1000 second. Even then, they were not completely frozen.
09-15-2010, 06:28 PM   #14
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Noblepa. You need to remember that in the 1/250 of a second is the opening time, closing time and the full open time. On the k10 and k20 there were complaints about max power at 1/180 and darkened lower portions of the image. This suggests to me the 540 duration in reality is longer than the K10/20 full open time.

I tried but pentax service would not give me the shutter times

Making 1/250 sync is no mystery the PZ1 did it almost 20 years ago and that was full frame. The blades had further to move
09-15-2010, 06:46 PM   #15
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QuoteOriginally posted by Lowell Goudge Quote
Noblepa. You need to remember that in the 1/250 of a second is the opening time, closing time and the full open time. On the k10 and k20 there were complaints about max power at 1/180 and darkened lower portions of the image. This suggests to me the 540 duration in reality is longer than the K10/20 full open time.

I tried but pentax service would not give me the shutter times

Making 1/250 sync is no mystery the PZ1 did it almost 20 years ago and that was full frame. The blades had further to move
I have no doubt that Pentax could make a shutter that synched at 1/250, if they choose to. I was only wondering how this could be affected by a firmware change.

The max sync speed of the K10D/K20D is 1/180. The documented flash duration for the 540 is 1/1200 - 1/20,000 second. Even if your suggestion is true and the shutter is not really fully open for 1/180 second (let's say half that, or 1/360), that's still almost four times the maximum duration of the 540. If someone is getting images clipped by the shutter, that would imply that the flash sync is happening too early or too late. I find it hard to believe that, at a stated speed of 1/180, the actual full-open time is less than 1/1200 second.


Paul
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