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06-04-2011, 11:04 AM   #1
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Pentax FA70-200 f4-5.6 what's the button on the side PA-AS?

Just picked up some Pentax gear that a guy was selling cheap, but had no answers to this question. What is the button PA AS for? I've been playing with it, but have not noticed any changes.

06-04-2011, 12:17 PM   #2
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QuoteOriginally posted by basquist02 Quote
Just picked up some Pentax gear that a guy was selling cheap, but had no answers to this question. What is the button PA AS for? I've been playing with it, but have not noticed any changes.
It is for power-zoom. Only works on some camerabodies.
06-04-2011, 12:52 PM   #3
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Should it work on the K7?
06-04-2011, 01:52 PM   #4
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QuoteOriginally posted by basquist02 Quote
Should it work on the K7?
No, I believe the power zoom function only works on certain 35mm film cameras.

06-04-2011, 02:14 PM   #5
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It should work on K20D, K-7 and K-5.
In some power zoom lenses you may have to shift the zoom ring forward or backward to engage the powerzoom, otherwise it only work like any manual zoom.
The buttons on the side of the lens break down quite easilly at least on the cheaper lenses.
Does it zoom manually if you turn the zoom ring?
06-04-2011, 03:11 PM   #6
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QuoteOriginally posted by Roob-N-Boots Quote
No, I believe the power zoom function only works on certain 35mm film cameras.
I mean the lens will work but the power zoom function won't.
06-04-2011, 08:21 PM   #7
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QuoteOriginally posted by Douglas_of_Sweden Quote
It should work on K20D, K-7 and K-5.
In some power zoom lenses you may have to shift the zoom ring forward or backward to engage the powerzoom, otherwise it only work like any manual zoom.
The buttons on the side of the lens break down quite easilly at least on the cheaper lenses.
Does it zoom manually if you turn the zoom ring?
It works with the zoom ring, but I don't think I have to worry about the side button any more as it just came off. Good thing it wasn't what I was after in the group of gear I purchased. Is it repairable if I should so desire?
06-04-2011, 08:23 PM   #8
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QuoteOriginally posted by Roob-N-Boots Quote
I mean the lens will work but the power zoom function won't.
This is incorrect, the power zoom function works on both the K-7 and the K-5. The contacts on the lens mount that now control SDM AF were once used for the power zoom. any body that has these two contacts will be able to drive the powerzoom.

06-04-2011, 08:52 PM   #9
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QuoteOriginally posted by wizofoz Quote
This is incorrect, the power zoom function works on both the K-7 and the K-5. The contacts on the lens mount that now control SDM AF were once used for the power zoom. any body that has these two contacts will be able to drive the powerzoom.
My bad.
06-04-2011, 09:04 PM   #10
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I'm a little confused. Can somebody please explain the purpose of a power zoom lens on an old 35mm body? I could understand applications on video cameras where a smooth, motor-controlled zoom would be useful. By why an old film camera? And HOW does one go about controlling power zoom on the K-7/K-5?
06-05-2011, 04:41 AM   #11
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On the top film cameras of that time you could do a couple of tricks with it, besides zooming atuomatically if you were lazy. It would retract itself to the focal lenght were the lens was the smallest size for storage when you turned it off. You could zoom while shooting for special effects. I presume that worked best on a little bit longer exposure times. Gave sort of a false impression of motion in the picture (and it got quite unsharp). I think you could also make it zoom to a pre-programmed focal length etc. But main thing was that you didn't had to zoom with your own muscel power. Me, it mostly annoyed since it is quite noicy. But I didn't get any zoom or autofocus lens until 1997, so obviously I was the wrong target group for this. My brother had a Z-1 with a powerzoom lens, but I can't remember that he found this very usefull. I recently got a 28-80 power zoom lens cheap to try to play with it on video, but the problem is that it is so noisy, so it really only work if I am to use the video without sound, or if I film something even noisier. Separate mic is a must. The power zoom makes much more noise than even the worst screw drive autofocusing. Supposedly besides the FA* lenses with power zoom, the only consumer quality lens worth having for its optical quality is the 28-105, my 28-80 and the 70-200 is supposed to be less than average.

Basquist, since your button fell off, I would think that it was the problem from the start. This is a known problem. I would suggest not to bother with it and use it as a normal lens...and the enjoy the rest of the stuff you bought.
06-05-2011, 07:29 AM   #12
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Doug,

Thanks for the explanation. Sounds like it was more of a gimmick than an actual useful feature.

But I'm still curious as to HOW you actually control the power zoom function. Is there a button on the lens, or was it controlled from the camera? And if it is controlled from the camera, how is it controlled from the K-7/K-5? I certainly don't remember hearing of any kind of dedicated power zoom buttons.
06-05-2011, 08:31 PM   #13
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QuoteOriginally posted by Douglas_of_Sweden Quote
Basquist, since your button fell off, I would think that it was the problem from the start. This is a known problem. I would suggest not to bother with it and use it as a normal lens...and the enjoy the rest of the stuff you bought.

Thanks. I mainly bought everything the guy had to get the f50 1.7, also got a SF10 a couple of close up filters and a hoya polarizer.
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