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10-08-2010, 12:19 AM   #1
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Remote flash

I have a K-x that I think is great, but I have one problem with it.
I would like to use remote slave flashes (not Pentax, but Vivitar) activated from the camera. I can do this by firing a small, low-power flash from the camera, but it would be more convenient to use the camera's built-in flash . . . but whatever I try the remote flashes won't synchronize with the shutter.

I think I've tried every combination of flash *including wireless flash possible, but it seems that there is always some sort of pre-flash (even with red-eye reduction 'off') that fires the remote gun(s) prematurely.

Can anybody help?

Thanks

10-08-2010, 01:03 AM   #2
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Well, that's how P-TTL works : it fires one pre-flash to meter the scene, then start the exposure and fires the main burst...
If you're using optical slaves, you don't have a lot of choices:
- use your lens in manual aperture. This will make the built-in flash fires at full power, without pre-flash. You can use a Nikon SG-3IR to cut down the built-in flash effect on your pic.
- use a RF flash trigger for one flash. They are cheap and work well.
10-08-2010, 08:08 PM   #3
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QuoteOriginally posted by Fulk Quote
I have a K-x that I think is great, but I have one problem with it.
I would like to use remote slave flashes (not Pentax, but Vivitar) activated from the camera. I can do this by firing a small, low-power flash from the camera, but it would be more convenient to use the camera's built-in flash . . . but whatever I try the remote flashes won't synchronize with the shutter.

I think I've tried every combination of flash –*including wireless flash – possible, but it seems that there is always some sort of pre-flash (even with red-eye reduction 'off') that fires the remote gun(s) prematurely.

Can anybody help?

Thanks
Probably not, sorry.

Although I do experience your same problem. Presumably your Vivitar flash is a DF383 model, correct?

For my K-x, I bought a Bower SFD926P (is P-TTL savvy, but not fully like a genuine - and is equiv of Vivitar 383) and also a (manual only) Yongnuo YN-460.
Both are affordable priced in their class and support optional off-camera Slave mode.

Like you I also can't reliably get the onboard flash to reliably cooperate, so have almost given up and plug the YN460 in the K-x hotshoe and point it at the remote Bower.
Unlike the onboard it's directional too so that's a plus, and doesn't support P-TTL so no real preflash tantrums to interfere.

Still have to cope with occasional misfires though, which is a real drag from the K-x not having any corded off-cam-flash option (100% reliable & faster sync), except lame IR wireless.
Even RF would be better.

The other serious limitation (as discussed in another topic here), is that K-x wireless Flash, and wireless Shutter release if on 3 secs timer, can't be used concurrently.
Enabling Remote Drive Mode (only on 3s) over-rides W.Flash.
Yeah doesn't make sense to me either but it sure cripples some opportunity, just enjoy the clashing mirror shake.

I really wish the Pentax manual would delve a little into explaining some of the more unusual (and therefore unfamiliar to most) functions and their behaviours that it only glosses over.
Would at least clarify its pluses or limitations and save much end-user frustration.

eg. DFS (Dark Frame Subtraction) is apparently a built-in, and one that causes much agro with many who want/need to disable it, but the feature gets absolute zero mention in the K-x manual. It's simply not explained, so users are left to wonder why their camera, after taking a long exposure, goes ahead and repeats the whole same length of time in re-exposure/processing (effectively unusable until it finishes) for no apparent reason.
I thank the Internet and forums like this where we learn truths about these mystery "features" existing.

Fwiw: In case you haven't read it, here's one site I found useful when info~researching prior to buying the flash units:
The Definitive Guide - Pentax P-TTL Flash Comparison

Apols again for being no real help to solve your problem.

.R.

Last edited by Hypocorism; 10-08-2010 at 08:56 PM. Reason: Reworded for clarity.
11-21-2010, 04:59 PM   #4
cas
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My two cents...

I got a Promaster FTD 7000M flash unit for Pentax. I tried to use it off-camera, triggered with the on-camera flash, with no luck. I was able to see the flash through the viewfinder (VF) but the pictures came our underexposed.

Then I realized the problem was the pre-flash of the P-TTL system: it was triggering the Promaster unit and that's why I was seeing the big flash in the VF, meaning it wasn't firing during the actual exposure.

The solution was to reduce the power output of the Promaster unit to 1/4 or less. By doing so, the Promaster actually fired during both pre-flash and the exposure-flash. Since low power flashes do not drain the charge completely after every flash, the unit can fire the pre-flash and be ready to flash again in femtoseconds, so it catches up with the exposure flash. At the beginning, when I was using full power, the batteries didn't get to charge the unit fast enough and always missed the exposure.

I am not a fan of not being able to use the full power of the Promaster flash, but at least it is a way around the problem until you get a RF system.

CAS

11-21-2010, 05:52 PM   #5
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I have some chinese RF triggers that do fine with my four old Vivitar 283s (and a few others) if I have a more elaborate flash setup, and I have this Sunpak optical trigger which can be set to ignore the preflash.
DSU01 Sunpak Digital Slave Unit with Preflash Cancellation, Multi Flash & Sync Socket The Sunpak works once you find the right setting for ignoring the preflash. It is not all that cheap.

An off-camera flash that uses wireless P-TTL is the easiest solution by far. For me, it just works.
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