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06-17-2013, 08:54 AM   #31
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QuoteOriginally posted by pentasonic49 Quote
When I tried out the high speed sync the strobing flash did not stop the motion but the 1/8000 sec shutter probably did. In this mode the flash power was greatly reduced and I can't think of many applications. Since my last post I have updated the firmware for the Metz (just because I could) after about half a dozen tries because there was no FTDI driver. Then by magic the driver appeared saying something about 64 bit Windows and everything worked. I would have used XP 32 bit if I had known.
I have tried to set the K5 shutter to higher than 1/180 with the Metz and it refuses even on manual shutter until I set the Metz to HSS

06-17-2013, 10:24 AM   #32
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QuoteOriginally posted by Digitalis Quote
Using a shutter speed of 1/250th when using flash as the sole light source with a shutter mechanism with a synch limit of 1/180th you Will see a black (unexposed) area. This isn't a question of proof, it is an inconvertible truth - if you had any idea how camera shutters work with flash you would know this.
The duration between the leading and trail shutter is the shutterspeed.
X-sync speed is the time that the leading shutter arrives and when moment later the trailing depart, at least that's the hardware limitation.

But how can you be sure that the 1/180 limitation is truly the hardware limitation?

I believe the 1/180 is purely a software restriction and not the absolute hardware limitation.

So once again, proof to me you get a black bar in the photo at 1/250.
You can give me official numbers if you like, like the distance and the speed the shutter moves in the K5.
06-17-2013, 11:05 AM   #33
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The ist ds and the K-01 here won't fire the ext flash above the 1/160th ( or with the AF360, the speed is turned down from a higher speed.
On the other hand the Olympus M43 and external simple flash is not inhibited above its sync speed of 1/160th.
So I wound the speed up progressively. 200, 250, 320, 400 are ok The shutter becomes visible at 1/500th.
06-17-2013, 05:23 PM   #34
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QuoteOriginally posted by Anvh Quote
I believe the 1/180 is purely a software restriction and not the absolute hardware limitation.
prove it.

06-18-2013, 04:59 AM   #35
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That "i believe" it's a software limitation.
No idea how you can prove a thought..

However you said clearly that you will see a black bar at 1/250, not that you think you will see one. You've showed nothing to back that claim up so far so i'm confused how you can be so sure?
That's why i keep asking because it's something that can be proved, it's not an opinion.

To be clear i've nothing to disprove your claim either but i'm not the one who said it so firmly
06-18-2013, 06:16 AM   #36
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QuoteOriginally posted by Digitalis Quote
The reason for my certainty is because I know how shutter systems work. I work with Canon and Nikon cameras and I do notice a drop in the GN when full synch speed is being used, the difference between 1/180th and 1/250th is only really important when you are using focal lengths at or above 200mm.
I agree there is not much difference between 1/180 and 1/250, but correct me if i am wrong here, that the canon and nikon systems offer full sync speed at both leading and lagging edge trigger, the pentax system cuts lagging edge sync by 1/2, somewhat implying that the flash duration (covering all power settings) is really in the range of 1/180th.
QuoteQuote:



Correct, the black bars will not be immediately visible. It is interesting to note that in practically all modern shutter units the shutter blades are only moving at roughly 7m/s which is around 25.2 Km/h (15.6Mp/h). The T.1* time of the Pentax AF540FGZ at 1:1 power is said to be around T.1=1/400. So using this knowledge I'm sure someone could figure out how much of the frame would be black, as things stand the hour is too late for me to accomplish such a task at present. Burning the candle at both ends has its drawbacks.

*T.1 times are more relevant when one is trying to stop fast motion, The T.5 time for the AF540FGZ @ 1:1 power is approximately 1/1200th.
note that full power duration of the AF540FGZ is not as high as you state,

if you trace back through the forum posts, and also try yourself at full power against a uniformly lit wall, you will start to see a black / darker area at the bottom of the frame as shutter speed is increased to maximum. it disappears at 1/150 but is definitely there at 1/180 (at least it was with the K10D). Perhaps later shutters are a little quicker, but the flash duration at full power of the 540FGZ is actually quite long.

I also note that when comparing similar shots when taken using my *istD and switching (day to day or when I have which ever flash available) it appears that shots taken with my AF500FTZ are sharper and do not exhibit the same level of motion blur compared to shots taken when using the AF540FGZ .

I have not studied this in detail, it is just an impression but it seems that full power when using the AF540 does not freeze the image in all cases.
06-18-2013, 01:21 PM   #37
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QuoteOriginally posted by Lowell Goudge Quote
I agree there is not much difference between 1/180 and 1/250, but correct me if i am wrong here, that the canon and nikon systems offer full sync speed at both leading and lagging edge trigger, the pentax system cuts lagging edge sync by 1/2, somewhat implying that the flash duration (covering all power settings) is really in the range of 1/180th. note that full power duration of the AF540FGZ is not as high as you state,

if you trace back through the forum posts, and also try yourself at full power against a uniformly lit wall, you will start to see a black / darker area at the bottom of the frame as shutter speed is increased to maximum. it disappears at 1/150 but is definitely there at 1/180 (at least it was with the K10D). Perhaps later shutters are a little quicker, but the flash duration at full power of the 540FGZ is actually quite long.

I also note that when comparing similar shots when taken using my *istD and switching (day to day or when I have which ever flash available) it appears that shots taken with my AF500FTZ are sharper and do not exhibit the same level of motion blur compared to shots taken when using the AF540FGZ .

I have not studied this in detail, it is just an impression but it seems that full power when using the AF540 does not freeze the image in all cases.
I have just tried to get the K100, K20 and the K5 to fire a Cobra Macroflash (non dedicated ringflash ) at speeds above 1/180 sec without success. My old manual Cosina C1 film camera will fire the flash up to 1/1000 sec but not at 1/2000. The C1 shutter is a mechanical metal vertical run with sync at 1/125. At 1/1000 sec the gap between the blinds when the flash fires is about 3mm at the top of the frame. I would love to know how to get a Pentax digital camera to fire a flash above the 1/180 speed. The only other flash I could try is an old Cobra auto-thyristor but with a trigger voltage of 239V it would not be worth the risk.
06-18-2013, 02:43 PM   #38
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QuoteOriginally posted by pentasonic49 Quote
I have just tried to get the K100, K20 and the K5 to fire a Cobra Macroflash (non dedicated ringflash ) at speeds above 1/180 sec without success. My old manual Cosina C1 film camera will fire the flash up to 1/1000 sec but not at 1/2000. The C1 shutter is a mechanical metal vertical run with sync at 1/125. At 1/1000 sec the gap between the blinds when the flash fires is about 3mm at the top of the frame. I would love to know how to get a Pentax digital camera to fire a flash above the 1/180 speed. The only other flash I could try is an old Cobra auto-thyristor but with a trigger voltage of 239V it would not be worth the risk.
It's not the flash units, it's the camera. Somewhere in the Pentax firmware there is a line of code that says something to the effect of:

IF (shutter_speed)
> 1/180th THEN disable sync signals

That's it. If that line of code weren't there, the flash would fire as soon as the first curtain opens, regardless of where the second shutter is in relation. In other words, you would get black bars. It's been that way for quite a while, my K20D does it, my Z-1p does it, but my old film KX doesn't. If someone were to hack the firmware, it might be possible to remove the offending line of code, but short of that, I don't think there's any way to make it work.

06-18-2013, 08:26 PM   #39
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QuoteOriginally posted by Lowell Goudge Quote
note that full power duration of the AF540FGZ is not as high as you state,
which is the reason I included the reference for the information I was working from. I'm not entirely sure of the actual duration myself.

QuoteOriginally posted by Lowell Goudge Quote
if you trace back through the forum posts, and also try yourself at full power against a uniformly lit wall, you will start to see a black / darker area at the bottom of the frame as shutter speed is increased to maximum. it disappears at 1/150 but is definitely there at 1/180 (at least it was with the K10D). Perhaps later shutters are a little quicker, but the flash duration at full power of the 540FGZ is actually quite long. I also note that when comparing similar shots when taken using my *istD and switching (day to day or when I have which ever flash available) it appears that shots taken with my AF500FTZ are sharper and do not exhibit the same level of motion blur compared to shots taken when using the AF540FGZ . I have not studied this in detail, it is just an impression but it seems that full power when using the AF540 does not freeze the image in all cases.
Interesting observation, I am more familiar with my Elinchrom studio equipment that has considerably shorter flash durations at 1:1 than hotshoe flashes, but I have noticed that the motion stopping capability of the AF540FGZ is not as good as other flash units capable of similar/greater power output e.g: Nikon SB900 Canon EX 580II.

QuoteOriginally posted by Anvh Quote
However you said clearly that you will see a black bar at 1/250, not that you think you will see one. You've showed nothing to back that claim up so far so i'm confused how you can be so sure?
Because of my knowledge of the mechanics of camera shutter systems. If the the sole light source is flash, and a shutter speed higher than the recommended synch speed is used, a blade of the shutter will be covering part the sensor while the flash is fired there will be a unexposed(black)area in the frame. The amount of the frame that will be unexposed depends on how far the recommended synch speed is exceeded.

PS:

As we all know, the hot shoe on pentax DSLR cameras goes cold when shutter speeds higher than the synch speed are used(without HSS enabled flash hardware) so I got my Pentax K5IIs and linked the shutter release remotely to my Nikon D4 which was set at its synch speed of1/250th which in turn triggered my studio strobes. After several attempts, this is what I got from my Pentax K5IIs with my sigma 180mm f/3.5 APO EX and a synch speed of at 1/250th with my Elinchrom BRX 500 fired at a blank wall @ 1:1 power*:



EXIF of this image is intact, I shot several frames some of which were black because of the fact that the shutter lag on the D4 is considerably lower than the K5IIs** - fortunately with the computer control capability of the Elinchrom BRX flash units you can set the flash units to delay firing after the synch signal has been sent for a set time, so using this control I was able compensate for the differential in shutter lag and get the timing perfect. I got some strange looks from my colleagues in the studio when I was doing this.

*Flash duration T.1= 1/520th
**D4= 45ms Vs K5IIs=90ms

Last edited by Digitalis; 06-18-2013 at 10:05 PM.
06-18-2013, 09:10 PM   #40
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QuoteOriginally posted by Digitalis Quote
Because of my knowledge of the mechanics of camera shutter systems. If the the sole light source is flash, and a shutter speed higher than the recommended synch speed is used, a blade of the shutter will be covering part the sensor while the flash is fired there will be a unexposed(black)area in the frame. The amount of the frame that will be unexposed depends on how far the recommended synch speed is exceeded.
Then how come I did not see this in the test I did on the Oly M43? (post #33 above)
06-18-2013, 09:44 PM   #41
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QuoteOriginally posted by wombat2go Quote
Then how come I did not see this in the test I did on the Oly M43
i'm not familiar with olympus cameras, but it is possible it uses an electronic( sensor based) shutter at longer shutter speeds - and a physical shutter at the shorter speeds. Which I have to say is a bit counter-intuitive, higher shutter speeds require the shutter to be more durable and to make it durable enough it has to be made of strong materials, which in turn that adds mass to the shutter and this makes it harder to move quickly. It makes more sense to have a physical shutter for the lower speeds and use an electronic one for faster speeds.

Last edited by Digitalis; 06-18-2013 at 10:03 PM.
06-18-2013, 10:19 PM   #42
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Do any M4/3 or dslrs have electronic shutter to date?
The Oly EPL1 has a "computerized focal plane shutter" which is easily viewed up to 1/500 s as a metal vertical run shutter, as it fires with the lens off.
The sync speed can be set between 1/60 and 1/160 by the user.
I tested with the old Pentax AF16 which is all done by 1.8 millisec at full power - and correspondingly faster if it quenches by the sensor feedback.
The camera fires the hot shoe even above the sync speed.
In my test the lower curtain was not visible at 1/400th and is visible at 1/500th ( 2 millisec) . This is well faster than the 1/160 sync speed.
06-19-2013, 02:35 AM   #43
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1/180 is just one of those limitations that you either live with or work around.

HSS isn't as useless as some people make out since you have considerable headroom with regards to ISO. For example, to shoot with flash at 1/1000 rather than 1/180, you'll get good exposure if you raise the ISO from 100 to 800.

Using an HSS-capable flash, it is possible to trigger a manual flash at extreme shutter speeds using the manual flash in optical slave mode. Here's the result of an experiment with just such a setup taken at 1/4000:



The manual flash on the tripod is a Lumopro LP160 at full power. No idea the degree to which this will work with any slaved flash. I think that Lumopro must have an extremely long T-time for this to be even possible.
06-19-2013, 04:49 AM   #44
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QuoteOriginally posted by top-quark Quote
Here's the result of an experiment with just such a setup taken at 1/4000:
Wow. 1/4000 and you have a viable flash exposure. Interesting.
06-19-2013, 06:33 AM   #45
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QuoteOriginally posted by rawr Quote
Wow. 1/4000 and you have a viable flash exposure. Interesting.
while using HSS of course.
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