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08-08-2011, 11:34 PM   #1
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K-5 and zoom lens questions...

When I mount my Sigma 70-300mm APO lens, the K-5 sometimes throws up the screen that requests focal length input... the same one that pops up when I mount the old primes. (In this case it throws up the 135mm measure???) Why is it doing this... and do I actually have to select a focal length number for it? I thought the camera is supposed to access this info automatically?

Another question relating to this: What measure does one put in for an old zoom lens - Pentax or third party? I am assuming its the maximum zoom limit of the lens. Appreciate any feedback.
Thanks, Nogster

08-09-2011, 12:04 AM   #2
Ash
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You shouldn't have to set a focal length on this lens. Ensure your lens contacts are clean and the lens is mounted properly before switching the camera on.

For zoom lenses, you choose how you want to influence the shake reduction mechanism. Set it to the highest focal length, and it starts kicking in at shutter speeds slower than approximately 1/(focal length). This would ensure all focal lengths are covered in slow shutter speed handheld shots. Some users choose halfway between to get the best of both worlds - totally up to you.

As this is more of a beginner's question, I have moved this to the Beginner's Q&A corner. Also, the title of the thread does not correlate to either of your questions. I have changed it slightly to reflect this. Please consider this next time you post.
08-09-2011, 12:52 AM   #3
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Sigma 70-300 is crappy lens, probably misbehaving. Any AF lens should report the FL correctly. For manual zooms I recommend not to use them. Usually not worth it. For the ones that are worthy (smc-A70-210...) better input the lower end (70mm). Undercompensating the shake does infufficient improvement, but overcompensating it actually hurts the IQ.
08-09-2011, 02:13 AM   #4
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I've had this happen once or twice using Sigma lenses. Re-mounting the lens has always corrected it. One thing that can cause this is forgetting to turn the camera off before attaching a lens.

The Sigma 70-300 is just fine, for its price. It's a hellova lot better than the Tamron 70-300. Of course individual copies of either will vary somewhat.

08-09-2011, 09:14 PM   #5
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I've never had that happen to be but the only thing I can think of that would cause that are dirty contacts or maybe a short in on of the lens contacts. Clean the contacts and if it continues it might be in the lens.
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