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08-09-2011, 10:10 PM   #1
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Why no SR for wireless flash?

Not that I really needed Shake Reduction, but I am just curious to know why my K20d automatically disabled SR when I used a Pentax AF 540 FGZ flash triggered wirelessly by the on-board pop-up flash in controller mode?

I don't understand flash much but I've used it before with better than moderate amounts of success, but noticed for the first time tonight that the SR was off on the photos I took in that mode.

I then switched to non-wireless mode and SR automatically kicked in!

I am certain it is by design but why?


Last edited by EsBee; 08-10-2011 at 08:16 AM.
08-10-2011, 12:16 AM   #2
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Good question. I wish I knew the answer. It does the same thing with the other cameras too.

08-10-2011, 12:38 AM   #3
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One less thing to complicate flashed exposure. But why it should be offered with hotshoed flash and not wireless is not quite clear to me.

I think it's a good idea to prevent unwanted sensor adjustment when dragging the shutter for a panned shot, but I suppose those who want to take night portraits would find use for SR. In those situations, I'd suggest a tripod anyway.

But if you really want SR on an off-camera flashed exposure, you'll just have to make do with a hotshoe extension cable...
08-10-2011, 03:28 AM   #4
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one of the many advantages of using a wireless radio trigger* for strobist work...


*I love my pocket wizards.

08-10-2011, 08:28 AM   #5
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QuoteOriginally posted by Ash Quote
One less thing to complicate flashed exposure. But why it should be offered with hotshoed flash and not wireless is not quite clear to me.

I think it's a good idea to prevent unwanted sensor adjustment when dragging the shutter for a panned shot, but I suppose those who want to take night portraits would find use for SR. In those situations, I'd suggest a tripod anyway.

But if you really want SR on an off-camera flashed exposure, you'll just have to make do with a hotshoe extension cable...
This is what the K20d manual says on Page 66 of the PDF file:

"The Shake Reduction function automatically turns off in the following situations:
When using self-timer, 2 sec. self-timer, remote control shooting, 3 sec. delay shooting, bulb shooting, or wireless mode with an external flash."

The guide doesn't say why, or at least I haven't found it yet. The other situations make sense because they all assume the camera is stable enough on a tripod or something similar, but I don't see any difference between using an external flash on the hot-shoe vs. in wireless mode.
08-10-2011, 09:29 AM - 1 Like   #6
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QuoteOriginally posted by EsBee Quote
This is what the K20d manual says on Page 66 of the PDF file:

"The Shake Reduction function automatically turns off in the following situations:
When using self-timer, 2 sec. self-timer, remote control shooting, 3 sec. delay shooting, bulb shooting, or wireless mode with an external flash."

The guide doesn't say why, or at least I haven't found it yet. The other situations make sense because they all assume the camera is stable enough on a tripod or something similar, but I don't see any difference between using an external flash on the hot-shoe vs. in wireless mode.
SR is turned off with the timer, remote, and bulb shooting because it is assumed you are using some sort of a mount (tripod or other) in those situations. Supposedly, the SR mechanism would be trying to correct for movement that isn't there and as a result, would blur your images. It really doesn't make complete sense because you can use a tripod without using any of those features.

It makes absolutely no sense to partially cripple the wireless feature. I can see where a tripod might be used with it (studio portraits for instance) and you would want SR off but it is also nice to be able to carry the camera around and, use wireless flash without the need for extra equipment (triggers) or being tethered to a cable. One of the things I've always liked about the Pentax cameras is they allow the User to make all of the decisions. For those who do not want to, there's always green mode. I would actually prefer it if, turning SR on or off was a completely Manual decision. That is, regardless of shooting mode, etc, allow the user to decide.

My 2

08-10-2011, 11:35 PM   #7
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Guessing on hardware limitation

I'm guessing here, but maybe the camera lacks processing horsepower to do both shake reduction and wireless p-ttl calculation and flash pulsing simultaneously. Or it lacks that last bit of battery power supply to make SR+wireless work reliably in all circumstances.

Wireless flash and shake reduction would be a very useful combination indeed. It's a shame it's disabled. I think the real reason is due to some kind of undesired hardware limitation. Only the Pentax engineers know for sure.

Regards,
--Anders.
08-12-2011, 11:41 AM   #8
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Probably CPU time would be my guess.
The probably thought it was ok because flash will "freeze" action as long as your ambient isn't too high...take a photo of a house fan w/ the flash on and your shutter speed at 1/30sec to see what I mean...

08-12-2011, 08:58 PM   #9
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QuoteOriginally posted by kenyee Quote
Probably CPU time would be my guess.
The probably thought it was ok because flash will "freeze" action as long as your ambient isn't too high...take a photo of a house fan w/ the flash on and your shutter speed at 1/30sec to see what I mean...
I know that part about freezing the motion with flash, it would do that even at slower shutter speeds. But what I don't understand is why the discrepancy of Shake Reduction between whether the flash is ON the camera or OFF. That just doesn't make any sense to me.

And what do you mean by CPU time?
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