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08-19-2010, 08:22 PM   #1
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K-x shake reduction with non-Pentax Zoom lenses

Dear All,

In manual of K-x I read that for non-compatible lenses you need to set the focal length in the camera to that of the lens (or the closest one).
- Are lenses like Sigma 50-150 F2.8 compatible, or should I for effective usage of shake reduction set it per zoom length?!?!?!

Best regards,

Joep

08-19-2010, 08:46 PM   #2
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That lens should work normally, as your camera can read the focal length being used. It is older lenses without the electrical contacts that will make you set the SR focal length.
08-19-2010, 10:23 PM   #3
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OK, thanks!!!
08-20-2010, 03:53 AM   #4
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SR will work with any lens, even ones that don't have electrical contacts, you just have to input the focal length manually. Unfortunately for zoom lenses that don't have contacts, you have to input the shorter end to the camera and therefore it doesn't work quite as well at the longer end. That Sigma should be fine.

08-20-2010, 05:10 AM   #5
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Rondec, not quite accurate - the general advice is to input the focal length that is halway between the long and short end of the lens - this is an obvious compromise but not a bad one.
08-20-2010, 08:37 AM   #6
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Or set it at the focal length you are planning to use. You can also set it again by switching the cam off and on again or going to menu 4 and set the correct focal length.

Anyway, every lens you can mount on you're camera can be used with the shake reduction, even an old Takumar M42 lens (mounted trough a KM adapter) of the early sixties
08-20-2010, 06:53 PM   #7
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QuoteOriginally posted by Sakura Quote
Anyway, every lens you can mount on you're camera can be used with the shake reduction, even an old Takumar M42 lens (mounted trough a KM adapter) of the early sixties
1960s aren't the limit. I have MF (medium format) and LF (large format) lenses from the 1910's and earlier that I mount in a bellows, set to the designated focal length, then switch SR on. Works like a charm! I'll also stick any other optical material I can into the bellows, like magnifier and eyeglass lenses, multifaceted crystals, etc. If I can get any sort of an image, and thus determine a focal length, then I can SR that too.
08-20-2010, 09:02 PM   #8
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Ever used a cow's eye?

08-20-2010, 09:41 PM   #9
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QuoteOriginally posted by jlaubza Quote
Rondec, not quite accurate - the general advice is to input the focal length that is halfway between the long and short end of the lens - this is an obvious compromise but not a bad one.
I tried to look up to see if this was true and couldn't find anything in the manual. However, my understanding is that if you aren't going to input a different focal length every time you zoom or pull back, you should use the wide end. The reason is that if you have too long a focal length set as compare to your actual focal length, the SR may actually add blur to your photo, by over compensating, whereas, if you have a focal length that is too short, it may not work as well, but it won't add any extra blur to the photos.
08-20-2010, 10:11 PM   #10
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Why is blur (a little too good/much) different from not as good?
- I would use focal length (or close to) of most critical length in zoom range (probably the long end)
08-20-2010, 10:12 PM   #11
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Right, but you'd have to overstate the focal length by kind of a lot - say, a factor of two or more - before SR starts being counterproductive. So in practice, I think it probably best to set a focal length maybe a quarter of the way into the zoom range in a typical 3x zoom - doesn't overstate by too much on the short end, and comes a little closer at the long end.

Last edited by Marc Sabatella; 08-21-2010 at 12:50 PM.
08-21-2010, 05:11 AM   #12
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QuoteOriginally posted by RioRico Quote
1960s aren't the limit. I have MF (medium format) and LF (large format) lenses from the 1910's and earlier that I mount in a bellows, set to the designated focal length, then switch SR on. Works like a charm! I'll also stick any other optical material I can into the bellows, like magnifier and eyeglass lenses, multifaceted crystals, etc. If I can get any sort of an image, and thus determine a focal length, then I can SR that too.
Would like to see you're setup for that, how you manage to mount a piece of broken glass in a bellow

And of course would like to see some results

Last edited by Sakura; 08-21-2010 at 05:48 AM.
08-21-2010, 11:41 AM   #13
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QuoteOriginally posted by JoepLX3 Quote
Ever used a cow's eye?
Good idea! I'll check with the local cows for volunteers!

QuoteOriginally posted by Sakura Quote
Would like to see you're setup for that, how you manage to mount a piece of broken glass in a bellow
I have several cheap (matched) sets of PK macro tubes, the sort with mount adapters and generic tube sections. ID (inner diameter) at the narrow end is 42mm of course; at the wide end, it's 57mm. So any material less than 58mm in two axes / dimensions can be shoved in there, held in place with tape if necessary.

QuoteQuote:
And of course would like to see some results
They're mostly pretty horrible. Try it and see!
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