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05-26-2012, 06:27 AM   #1
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High Speed flash sync?

recently i learn about using flash as fill light during daytime.
high speed sync is required since the shutter will be too fast for the flash.

but i been through the menu and didn't find anything related to this.
does the k5 comes with this function? or is it only available on canikon camera?

thanks.

05-26-2012, 06:38 AM   #2
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Your flash has to support HSS - if it does, you select this feature on the flash head...
05-26-2012, 07:47 AM   #3
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hss is available from most camera manufacturers, typically from the high end first party flash unit
05-26-2012, 08:40 AM   #4
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oh thanks.
so it is depends on the flash and not the camera.

05-26-2012, 08:52 AM   #5
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QuoteOriginally posted by telly0050 Quote
oh thanks.
so it is depends on the flash and not the camera.
Most if the time, not sure what other brands do with their entry level cameras but with Pentax all recent (4 years) DSLR can do it.
05-26-2012, 09:38 AM   #6
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All of the above mentioned posts are accurate, but... True high speed flash can be done on cameras that are unfortunately outside of the Pentax line. I've already worked with a few where on can sync the flash to over 1/2000th and much higher, but also try to imagine how much light is needed on that one. One could also technially use a well darkened room and then keep the shutter opend and then have the flash synced to the type of pic - for instance to simulate a truly high speed shutter/flash combination.

With ideal equipment or being a bit creative one can use flash to stop most anything.
05-26-2012, 09:53 AM   #7
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QuoteOriginally posted by telly0050 Quote
recently i learn about using flash as fill light during daytime.
high speed sync is required since the shutter will be too fast for the flash.

but i been through the menu and didn't find anything related to this.
does the k5 comes with this function? or is it only available on canikon camera?

thanks.
Yes, but its not the "shutter that to fast for the flash" actually the flash is always faster than the shutter (it fires in something like 1/10,000th sec)

The shutter speed will be too fast for the shutter curtains to be fully open across the whole frame when the flash goes off.
You can look up how shutters work but basically its like this.

A curtain comes down to let light into the sensor, when the shutter closes after the time you set (shutter speed) , ANOTHER (2nd) curtain comes down to block off the light to the sensor.

With Pentax the shutters travel across the sensor in a bit less than 1/180th sec. So if your shutter speed is 1/180 then the first curtain comes down and travels whole length of the sensor (so it is fully open across the whole frame) and then just after that the second curtain comes down to block the light off again.

At 1/180s it is only FULLY OPEN for a small instant, and that is when the flash triggers, either just when the first curtain makes it to the bottom or just before the 2nd curtain starts to move. The whole sensor is exposed and the flash lights it all over.

If you have the shutter speed at say 1/4000th sec. Then the first curtain starts coming down to open it and then 1/4000s later the second curtain comes down to block it off again BEFORE the first curtain has travelled fully across. What you effectively get is a small "slit opening" moving downwards across the sensor. Both curtains are still moving at the same speed as they always do but the delay between them is 1/4000s of course.
If you popped the single flash in there you would only get the flash to expose the "slit" that was across the sensor at that time & that's no good.

The answer is the High Speed Sync (as Pentax Calls it) but it works the same on Canikons etc..
The flash has to be able to do it and the camera also has to support it.

What the flash does is to actually spread out its discharge instead of one bright flash for 1/10000s or so, it has to emit several pulses of light that will expose the sensor as that "slit" in the shutters moves down the sensor. The flash is actually emitting pulses of light for about 1/180s total time in order to progressively light the sensor for only 1/4000s shutter speed (sounds odd but it does)

K5 supports HSS and many flashes also do it (mainly the expensive ones). The built in flash does not so you are limited to 1/180 with that one. and if you trigger a external wireless flash optically with the built-in then of course 1/180 is as fast as you go.
Another thing about the HSS mode, I sucks power. Your flash power is reduced alot because of the pulsing light emitting for a longer time instead of just 1 single flash.

.
.
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If my shutter explanation wasn't unsderstandable i found this on YT showing a hi speed video of the shutter curtains, could have save myself all that typing above.


its a Canon 5D so at 1/200 the sensor is fully exposed, at 1/1000s you can see there is only a slit moving down


Hope that might be helpful
05-26-2012, 10:15 AM   #8
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QuoteOriginally posted by Medium FormatPro Quote
All of the above mentioned posts are accurate, but... True high speed flash can be done on cameras that are unfortunately outside of the Pentax line. I've already worked with a few where on can sync the flash to over 1/2000th and much higher, but also try to imagine how much light is needed on that one. One could also technially use a well darkened room and then keep the shutter opend and then have the flash synced to the type of pic - for instance to simulate a truly high speed shutter/flash combination.

With ideal equipment or being a bit creative one can use flash to stop most anything.
You can use the fastest shutter speed with Pentax camera, with the K5 that is 1/6000th so don't know were you're getting your information from



Also to at to steve1307 story

HSS is great for fill light on a bright day but if you want to freeze fast movement, a drop falling for example you need to use the normal flash mode in a darkend room.
The single flash pulse is a lot faster and really freeze the movement while with a serie of pulses you get montion blur.

05-26-2012, 11:34 AM   #9
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thanks for all the information guys.
i currently have a yongnuo 560 ii which does not support hhs.
thinking of getting a AF 360, it's selling for 150 used on amazon.
i believe it is the cheapest solution for hhs so far?
05-26-2012, 01:07 PM   #10
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Look at the metz solution, the Metz 50 is the same price as the af360 and just as powerful but it has a swivel head.
Big bonus if you want to bounce the light indoors.
05-27-2012, 12:28 PM   #11
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The cheapest solution is a good ND filter... This way you can lower your shutter speed below the 1/180 x sync, and you'll save some flash power (HSS is eating quite a lot of power).

As you're trying to fight a strong ambient light, the darkened viewfinder should not be too troublesome...
05-27-2012, 01:15 PM   #12
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QuoteOriginally posted by dlacouture Quote
The cheapest solution is a good ND filter... This way you can lower your shutter speed below the 1/180 x sync, and you'll save some flash power (HSS is eating quite a lot of power).
But ND also eats flash power and it's not variable so you either need to buy expensive variable ND with his limitations or several ND filters.
All in all it's more troublesome then HSS if you ask me...
05-27-2012, 05:02 PM   #13
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QuoteOriginally posted by Anvh Quote
You can use the fastest shutter speed with Pentax camera, with the K5 that is 1/6000th so don't know were you're getting your information from
If you didn't know, the fastest shutter speed on the K-5 is 1/8000 sec. It is 1/6000 sec on the Pentax Kr.
05-27-2012, 05:39 PM   #14
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the metz 50 seems good, but i guess i would stick with af360 since im using wireless trigger 99% of the time.
plus i like the interface and buttons of af360 more.
thanks for your suggestion tho.
05-27-2012, 06:59 PM   #15
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QuoteOriginally posted by dlacouture Quote
The cheapest solution is a good ND filter... This way you can lower your shutter speed below the 1/180 x sync, and you'll save some flash power (HSS is eating quite a lot of power).

As you're trying to fight a strong ambient light, the darkened viewfinder should not be too troublesome...
QuoteOriginally posted by Anvh Quote
But ND also eats flash power and it's not variable so you either need to buy expensive variable ND with his limitations or several ND filters.
All in all it's more troublesome then HSS if you ask me...
Thinking about it ISO 80 on the K-5 and 1/180s a f2.8 is about EV11 which is pretty bright.
With a 3 stop ND you can shoot f2.8 to f4 in EV14-15 bright sunlight, so that's not too bad.

The YN-560 at 1/1 is only a bit less powerful then the AF540 at 1/1 according to the table I have on it.

Without an ND filter in the same condition you'd have to shoot at about 1/1500 and using the table in my AF-540 manual the HSS flash only carries a just about 1/2 to 2/3 the distance of the full power flash through a 3 stop ND.
Not sure if I worked it out accurately* (and someone who's test this please correct me if i'm wrong) but using HSS is singificantly less powerful than fitting ND's in the same situation.

I think if I were to buy a flash and intended to use it with HSS then it would be the most powerful one I could find (or afford). Or to put it another way, HSS on a low powered flash is pretty much useless if it wont carry any distance.


* I just compared tables of the GN of 1/8 power (=1/1 power with 3stops reduction) with HSS mode GN @1/1500 (which is 3 stops from 1/180 sync speed).
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