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02-08-2012, 06:45 AM   #1
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Bad wireless flash lighting

I'm experimenting with my Pentax K-r and an old Vivitar 2800 Thyrisitor Flash.
The flash is mounted on a Seagull Infrared Flash Remote Trigger and is set on manual.

I set the Kr on flash- wireless.
All I get is poor lighting when I compare with the internal Kr flash, same aperture, same speed.

Could it be the Vivitar that is too old?
Any idea?
Thanks

02-08-2012, 07:18 AM   #2
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That trigger appears to be a simple optical slave (when it sees a flash, it triggers the attached flash). As such, it will trigger when it sees a flash, whether that be from a main flash or a p-ttl pre-flash. I suspect thats whats going on here. In wireless mode, the on-board flash sends out a quick signal via a series of flashes to its p-ttl slave flashes about what power to be and all that junk. Your cheap optical slave is probably triggering during this instead of during the time that the shutter is open. Then you are just getting the weak on-board wireless master flash (rather than an actual flash) in your exposure. But all this is just conjecture without an example.
02-08-2012, 07:23 AM   #3
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The wireless mode in your K-r is not designed to trigger IR slaves, it's designed to trigger Pentax dedicated P-TTL flashes such as the 360 FGZ or the 540 (or several Metz models with wireless slave mode for Pentax). In this case you would need the IR transmitter for the seagull system. Even if your flash fires the IR slave, it will most likely not sync properly because the flash on your camera will fire pre-flashes to send the TTL metering info, causing the slave to fire prematurely.
02-08-2012, 08:00 AM   #4
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just forgo the use of wireless flash, and fire your flash normally, all will be well

02-08-2012, 08:01 AM   #5
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(it should work with the optical slave too) to clarify , fire your on-board flash as normal, and the vivitar with the trigger should fire at the right time.
02-08-2012, 10:26 AM   #6
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QuoteOriginally posted by Andrew Lang Quote
(it should work with the optical slave too) to clarify , fire your on-board flash as normal, and the vivitar with the trigger should fire at the right time.
The onboard flash will ALWAYS fire in P-TTL mode, there is no manual mode. For this reason it wil ALWAYS fire at least one preflash for metering purposes, unles you can configure the optical slave to ignore the pre-flash it will never sync. This happened to me while trying to sync with studio strobes with optical slaves, unless I configured the strobe to ignore the pre-flash it never synced.
02-08-2012, 03:42 PM - 1 Like   #7
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You can get the onboard flash to fire in manual flash mode without P-TTL if you use a lens with an aperture ring. If it is on any setting other than A, no preflash will fire. On the downside, your onboard flash will blast your subject at full force. You could suppress it with a fully exposed piece of film taped to the flash. The slave flash will still fire.
02-08-2012, 04:27 PM   #8
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QuoteOriginally posted by karpati Quote
You can get the onboard flash to fire in manual flash mode without P-TTL if you use a lens with an aperture ring. If it is on any setting other than A, no preflash will fire. On the downside, your onboard flash will blast your subject at full force. You could suppress it with a fully exposed piece of film taped to the flash. The slave flash will still fire.
Hmmm, I did not know that, but sure, it makes sense, with no A setting it can't do P-TTL metering... Thanks, learned something new!

02-08-2012, 05:33 PM   #9
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QuoteOriginally posted by karpati Quote
You can get the onboard flash to fire in manual flash mode without P-TTL if you use a lens with an aperture ring. If it is on any setting other than A, no preflash will fire. On the downside, your onboard flash will blast your subject at full force. You could suppress it with a fully exposed piece of film taped to the flash. The slave flash will still fire.
on the nose!

You can also use get a set of cheap radio transmitters.

I have the Cowboy Studio $28 set and they work really great.
02-08-2012, 05:43 PM   #10
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It's a bargain!

QuoteOriginally posted by mtroute Quote
on the nose!

You can also use get a set of cheap radio transmitters.

I have the Cowboy Studio $28 set and they work really great.
Will it work with my old Vivitar 2800? Matt's Classic Cameras: Vivitar 2800 flash
Is it required to use the Sync Wire Cable ?
I don't see any cable connection on the Kr

Tx
02-08-2012, 05:48 PM   #11
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QuoteOriginally posted by karpati Quote
You can get the onboard flash to fire in manual flash mode without P-TTL if you use a lens with an aperture ring. If it is on any setting other than A, no preflash will fire. On the downside, your onboard flash will blast your subject at full force. You could suppress it with a fully exposed piece of film taped to the flash. The slave flash will still fire.
Thanks, it's a nice explanation.
I tried with my old k1000 50mm lens and it works as you said. The onboard flash blast indeed!
But, in the end, that's what I need.
Thanks again!
02-08-2012, 06:01 PM - 1 Like   #12
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P-TTL without A setting

QuoteOriginally posted by jase036 Quote
Hmmm, I did not know that, but sure, it makes sense, with no A setting it can't do P-TTL metering... Thanks, learned something new!
Actually you CAN do P-TTL flash with a manual lens or A lens set at a specific f-stop. This is just the opposite of what the original poster wanted, but it can be done.

If you look at the K-r lens mount, you will see that the 3rd contact from the left (lens locking pin) side is indented rather than sticking out. Look at the mount of a K-A lens with it set on A versus any fixed f-stop value. You will see the matching contact retracts when not on A. So we can force the K-r to think it always has an automatic aperture on any lens by shorting this indented pin.

The slickest way to do this (not my idea by the way) is to remove the lens mount from the camera and place a thin strip of several layers of aluminum foil (2-4 depending on the foil) over the pin. Reinstall the mount (it will work like a paper hole punch) and trim any excess. It takes less than 5 minutes and a jeweler's screwdriver. (okay it took me 10 minutes the first time)


What happens is really useful.
  • First, you can manually set a lens aperature and because the camera thinks every lens has an automated aperature, flash will be P-TTL.
  • Second, if you manually set a f-stop, manual metering will normally just show "F _ _ _", except with the pin shorted, your camera will display a f-stop and shutter speed ... the operator's chore is now to make sure what the camera says will be the f-stop and where the lens is manually set are the same. Now program the green button to stop down the lens so you can see depth of field in the viewfinder. WOW! it's almost like shooting with a K-1000 and match needle metering.
What to return to how Pentax programmed your K-r? (can't imagine why, but...) Just remove the foil you installed.
02-08-2012, 06:06 PM   #13
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QuoteOriginally posted by S3rgio Quote
Will it work with my old Vivitar 2800? Matt's Classic Cameras: Vivitar 2800 flash
Is it required to use the Sync Wire Cable ?
I don't see any cable connection on the Kr

Tx
It will work with any hotshoe flash out of the box. they have optional cables for lights that need it. The trigger is actually radio controlled, so it will send an RF signal out and trigger the flash remotely. the transmitter slide into the hotshot on the K-r and triggers when the shutter is released. You do have to shoot in M mode on the K-r but a couple test shots and you should be able to get the exposure right on.
02-08-2012, 06:15 PM   #14
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QuoteOriginally posted by mtroute Quote
It will work with any hotshoe flash out of the box. they have optional cables for lights that need it. The trigger is actually radio controlled, so it will send an RF signal out and trigger the flash remotely. the transmitter slide into the hotshot on the K-r and triggers when the shutter is released. You do have to shoot in M mode on the K-r but a couple test shots and you should be able to get the exposure right on.
Ok, but i mesured on the Vivitar 2800 153 volts !
About what others mesured on: Photo Strobe Trigger Voltages

On Cowboystudio web site it says:
"Other flash models with a trigger voltage of 12V or lower"
02-08-2012, 06:45 PM   #15
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QuoteOriginally posted by JimJohnson Quote
Actually you CAN do P-TTL flash with a manual lens or A lens set at a specific f-stop. This is just the opposite of what the original poster wanted, but it can be done.

If you look at the K-r lens mount, you will see that the 3rd contact from the left (lens locking pin) side is indented rather than sticking out. Look at the mount of a K-A lens with it set on A versus any fixed f-stop value. You will see the matching contact retracts when not on A. So we can force the K-r to think it always has an automatic aperture on any lens by shorting this indented pin.

The slickest way to do this (not my idea by the way) is to remove the lens mount from the camera and place a thin strip of several layers of aluminum foil (2-4 depending on the foil) over the pin. Reinstall the mount (it will work like a paper hole punch) and trim any excess. It takes less than 5 minutes and a jeweler's screwdriver. (okay it took me 10 minutes the first time)


What happens is really useful.
  • First, you can manually set a lens aperature and because the camera thinks every lens has an automated aperature, flash will be P-TTL.
  • Second, if you manually set a f-stop, manual metering will normally just show "F _ _ _", except with the pin shorted, your camera will display a f-stop and shutter speed ... the operator's chore is now to make sure what the camera says will be the f-stop and where the lens is manually set are the same. Now program the green button to stop down the lens so you can see depth of field in the viewfinder. WOW! it's almost like shooting with a K-1000 and match needle metering.
What to return to how Pentax programmed your K-r? (can't imagine why, but...) Just remove the foil you installed.
Wow, that is awesome, I almost feel tempted to try it, but for me, I do a lot of multiple off camera flash and strobe lighting and always use manual everything with radio triggers. Even when I mount my Metz 48 AF-1 on the camera I don't use P-TTL, I use manual... I like to have more control, especially when I'm bouncing off walls or ceiling.
Still I might set up my K200D like this and leave the K-5 normal just for fun
Thanks a lot for sharing that info!
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