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03-17-2010, 06:30 PM   #1
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K-x lens mount with old k-mount lenses

Does the Pentax K-x accept the lenses that work with my old 35mm K-1000?

From the pentax website it says that the K-x has the following lens mount:
LENS MOUNT:
Type/construction: PENTAX KAF2 bayonet stainless steel mount
Usable lenses: PENTAX KAF3, KAF2, KAF, KA (K mount, 35mm screwmount, 645/67 med format lenses useable w adapter and/or restrictions)
SDM function: Yes
Power zoom function: n/a
Will my old "Fisheye MC Zenitar-K (Pentax) 16mm f/2.8", which fits on my K-1000, mount on a new K-x?

See here:Fisheye MC Zenitar-K (Pentax) 16mm f/2.8

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03-17-2010, 06:36 PM   #2
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Yes, but fish-eye lenses don't give much fish-eye effect on clipped sensor cameras. If you are used to thinking in terms of 35mm film, your Zenitar will look like a 24mm lens with really bad barrel distortion.
03-17-2010, 07:20 PM   #3
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See the first item (sticky) on the Beginner's Forum: https://www.pentaxforums.com/forums/pentax-beginners-corner-q/59272-shooting-...x-dslrs-f.html

QuoteOriginally posted by Wheatfield Quote
Yes, but fish-eye lenses don't give much fish-eye effect on clipped sensor cameras. If you are used to thinking in terms of 35mm film, your Zenitar will look like a 24mm lens with really bad barrel distortion.
Or, more pedantically, the Zenitar will have the same field of view (FOV) as a 24mm lens on your old K-car. The perspective and distortions will remain the same; you'll just see a smaller slice of the picture. I'd say the DOF remains the same too, but that'll just start arguments. Think of the old 36x24mm frame; lay a 25x17mm frame over the center; that's how much picture you'll get now.
03-18-2010, 11:19 AM   #4
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I see, so the "clipped sensor" in the K-x (which stands in place of the film on a regular 35mm camera) is a smaller rectangular frame than what is found on a 35mm film frame?

03-18-2010, 11:47 AM   #5
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QuoteOriginally posted by sipper Quote
I see, so the "clipped sensor" in the K-x (which stands in place of the film on a regular 35mm camera) is a smaller rectangular frame than what is found on a 35mm film frame?
Yes. The APS-C sensor in the Kx and other Pentax dSLRs (but not the new 645D) is sized as I said above, about 25x17mm, with an area about half that of a 35mm still frame (often referred to as FF or 35/FF). The APS-C is very close to the old half-frame 35/HF used in Olympus Pen-F SLRs and various Canon and other rangefinders. That's also the size of 35mm cine, but that's another subject.

But what's significant is the image circle a lens needs to project, to fill the frame, and that's based on the frame's diagonal. A 35/FF diagonal is 43mm. An APS-C or 35/HF diagonal is 29mm. The ratio is 1.5, which is what's called the Crop Factor. When you read that a 100mm lens on 35/FF becomes a 150mm lens on your Kx, that just refers to the size of what you see. That 100mm remains a 100mm lens in terms of perspective.
03-18-2010, 11:47 AM   #6
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QuoteOriginally posted by sipper Quote
I see, so the "clipped sensor" in the K-x (which stands in place of the film on a regular 35mm camera) is a smaller rectangular frame than what is found on a 35mm film frame?
Wow, you understood that faster than most people in the Beginner's Q & A
03-18-2010, 04:32 PM   #7
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What is good about this also is if a lens for a FF has soft corner focus, it will be clipped in the APS-C and you would have a better lens in effect without/or just a small amount of the soft corners.
03-18-2010, 05:08 PM   #8
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QuoteOriginally posted by sipper Quote
I see, so the "clipped sensor" in the K-x (which stands in place of the film on a regular 35mm camera) is a smaller rectangular frame than what is found on a 35mm film frame?
Fastest understanding of crop-sensors, ever.

03-18-2010, 05:40 PM   #9
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QuoteOriginally posted by RioRico Quote
Think of the old 36x24mm frame; lay a 25x17mm frame over the center; that's how much picture you'll get now.
QuoteOriginally posted by noahpurdy Quote
Fastest understanding of crop-sensors, ever.
Hey, don't I get credit for explaining it clearly and succinctly?
03-18-2010, 05:45 PM   #10
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QuoteOriginally posted by RioRico Quote
Hey, don't I get credit for explaining it clearly and succinctly?
Leave it to the jealous ones to beg for credit.
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