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06-19-2011, 11:41 PM   #1
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First Dopey Question....

I am having fun learning about all the different things I can do with my new K-x, but
my first question is this:

When using a manual focus lens in most of the manual modes, the camera will always ask me to set the focal length before taking pictures. If I am using my
135mm Super Albinar do I set the focal length to 135 and so on for the different lenses?

Hope this is not a dopey question....

Thanks in advance!

Rick

06-20-2011, 12:11 AM   #2
Ash
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Yes, that focal length is what the camera uses to appropriately apply shake reduction.
06-20-2011, 12:37 AM   #3
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Aaaaaah..........

so if i use my 500mm tele lens......input 500mm focal length..........135 for135..
and so on.

Thanks so much
06-20-2011, 05:44 AM   #4
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QuoteOriginally posted by Kx-Rick Quote
Aaaaaah..........

so if i use my 500mm tele lens......input 500mm focal length..........135 for135..
and so on.

Thanks so much

Correct. Its one of the big advantages of the Pentax system using in-body shake reduction instead of lens-based image stabilization. Means we have shake reduction even for old lenses

06-20-2011, 08:47 AM   #5
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Good, you didn't fall into the crap.factor fallacy! The SR'bot wants to know the lens' actual focal length, or as close to it as possible.

What to look for next: If you use a teleconverter with a lens, enter the multiplied focal length. So if you had a 50mm lens with a 1.4x TC, you would enter 50x1.4= 70mm (if possible -- 75mm is close enough). For a 50mm lens with a 2x TC, you would enter 50x2= 100mm. Et cetera.

This works for all primes. Manual zooms are another matter. For best results, enter the focal length you are using. But if you zoom a lot, that gets tedious. Someone here posted a formula for approximating the best entry:
(2 * min * max) / (min + max)
where min is the zoom's minimum focal length, and max is its maximum. Of if that's all too tedious, just shoot manual zooms in bright light with a fast shutter and turn SR off. That's how we did it Back In The Day. If we had zooms, of course. Newfangled gadgets...
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