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05-25-2014, 02:19 PM   #1
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Help me understand remote triggering...

This may be a dumb question, but I'm not a DSLR old hand and this is my first flash experimentation. And as they say "there is no such thing as a dumb question, only dumb answers".
I was out today with a couple of friends doing some shooting. The idea was that we'd be doing remote triggering of flashes. My friend has a cheap Cowboy Remote Trigger, Amazon.com : CowboyStudio NPT-04 4 Channel Wireless Hot Shoe Flash Trigger Receiver : Camera Flash Accessories : Camera & Photo
and that is what we were planning to use. It worked on his Canon and the other friend's Canon full frame, but not on my K-3. I've done some browsing around the forum and the best explanation I've come up with is that though we were suppose to set our shutter speed to 1/250th, it is incompatible with Pentax, it shuts down flash capabilities at a shutter speed over 1/180th. I tested wiith my TTL flash with the shutter speed up and the camera just resets to 1/180th.
Am I correct in assuming that it does this because it is TTL and the camera "understands" it, where as the dumb trigger only has the one contact in the middle and the camera doesn't recognize this and just shuts down the hot shoe because of the shutter speed?
If I had reset my shutter speed to 1/180th would the trigger have just worked?
I thank in advance anybody who can help clarify all this for me.


05-25-2014, 03:02 PM   #2
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Pentax flash sync is set at max 1/180. the flash just won't fire above that shutter speed. This is one weakness of Pentax, most Canonikon will have 1/200 or 1/250 sync speed and even faster on top of the line FF. The camera reset to 1/180 because faster speed than this "might" cause black underexposed bands. This is because of the way a DSLR shutter works. Pentax probably measured the shortest travel time of their shutter curtain from top to bottom to be about 1/180, above that speed, the second shutter curtain will begin to drop, blocking part of the sensor during the flash burst. When using a flash, the sensor has to be completely exposed for it to work. ***unless using High Speed Sync, where the flash sends multiple low power burst instead of a longer high power one***
05-25-2014, 03:12 PM   #3
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QuoteOriginally posted by Catscradle Quote
Am I correct in assuming that it does this because it is TTL and the camera "understands" it, where as the dumb trigger only has the one contact in the middle and the camera doesn't recognize this and just shuts down the hot shoe because of the shutter speed? If I had reset my shutter speed to 1/180th would the trigger have just worked?
Almost correct. The camera will not fire the flash with a shutter speed over 1/180, it does not matter if it recognizes a flash or not. If the camera recognizes the flash, (either the pop-up flash or a P-TTL that it can communicate with.) the camera will automatically set the shutter speed to something that will work.

The actual "flash sync speed" varies between manufacturers and between cameras within the line. Pentax is slower than most others by a bit.
05-25-2014, 03:14 PM   #4
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QuoteOriginally posted by fgaudet Quote
Pentax flash sync is set at max 1/180. the flash just won't fire above that shutter speed. This is one weakness of Pentax, most Canonikon will have 1/200 or 1/250 sync speed and even faster on top of the line FF. The camera reset to 1/180 because faster speed than this "might" cause black underexposed bands. This is because of the way a DSLR shutter works. Pentax probably measured the shortest travel time of their shutter curtain from top to bottom to be about 1/180, above that speed, the second shutter curtain will begin to drop, blocking part of the sensor during the flash burst. When using a flash, the sensor has to be completely exposed for it to work. ***unless using High Speed Sync, where the flash sends multiple low power burst instead of a longer high power one***
Thanks for the info. Especially thanks for explaining the "why" of the "speed limit".

---------- Post added 05-25-14 at 06:18 PM ----------

QuoteOriginally posted by jatrax Quote
Almost correct. The camera will not fire the flash with a shutter speed over 1/180, it does not matter if it recognizes a flash or not. If the camera recognizes the flash, (either the pop-up flash or a P-TTL that it can communicate with.) the camera will automatically set the shutter speed to something that will work.

The actual "flash sync speed" varies between manufacturers and between cameras within the line. Pentax is slower than most others by a bit.
Thanks.

05-25-2014, 06:09 PM   #5
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Also to add to the other replies as it seems you have the K3.
On the mode dial you can set it to the red "X" position. This locks the camera into the max sync speed of 1/180 of the camera so you cannot accidently move the shutter speed over the limit imposed by Pentax. You can still adjust your aperture and ISO accordingly.
I use this setting fairly often while shooting flash as there is the odd occasion when I am using the camera in manual mode and I am left scratching my head as to why the flash did not fire and a few moments later I realise it was because I accidently hit the shutter speed dial and moved it over the max sync speed.
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