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04-08-2010, 06:22 AM   #1
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Effects of adapting lens?

I previously posted in a thread that there is no stores around me selling lenses. It occurred to me that I dismissed all the relatively close posted used lenses because they weren't for a newer model Pentax.

I'm not thinking. I don't mind MF if its a $30 lens! How many different mount styles are there for Pentax compatible lens? I know there is my style for the k20d, is that a "k mount"? And I know there is thread mount. If I get a thread to k style lens adapter, clearly it moves the lens further from the body. Dose this affect image quality? What about other lenses, can I get a Nikon lens and an adapter for that?

Realizing there are adapters and MF isn't so bad opened up a whole new world of locally available lenses for me!


Thank you,
-Shawn

04-08-2010, 06:27 AM   #2
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Going from other major brands (Canon, Nikon, etc.) to Pentax is possible in some cases and tricky, or totally impossible. You're better off sticking with Pentax K (all Pentax lenses will work on your camera), M42 screw mount (adapter needed), or third party (Vivitar, Tamron, etc.) made for Pentax K or M42.

You're better off going with ONLY M42 lenses and the adapter, because the K mount lenses will only operate wide open on your DSLR.
04-08-2010, 06:37 AM   #3
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What is the name of the mount for my k20d? If the k-mount only operates wide open is there an adapter for that also to make it manual aperture? I'm kicking myself now for selling my dad's pentax lenses a five years ago when I went Canon! 135 prime 200 prime and a handful of others!
04-08-2010, 06:45 AM   #4
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QuoteOriginally posted by smcook99 Quote
What is the name of the mount for my k20d? If the k-mount only operates wide open is there an adapter for that also to make it manual aperture? I'm kicking myself now for selling my dad's pentax lenses a five years ago when I went Canon! 135 prime 200 prime and a handful of others!
All K lenses will work on all K bodies, from the old days of film to today. But they will only shoot wide open.

This adapter here goes in your K20d (which is K), and lets your camera take M42 screw lenses, and you have full aperture usage:

PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet)

04-08-2010, 06:48 AM   #5
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If you look at my lens list below, the only two which aren't M42 screw mount are the 18-55 kit lens that came with my KX, and the 90 Macro Tamron.

All of the rest are old glass, so basically, my adapter is always on my camera.
04-08-2010, 06:53 AM   #6
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I apologize, I'm must be slow today, I'm having a hard time picking up on what you're saying about K-mount lenses.


You're saying that all K-mount lenses will work on my camera but only shoot wide open. So lets rule out all the M42 for a second and run with that. You said my k20d is a K-mount. I just got a Tamron 28-75 f2.8 which fits my k20d and so I assume it's a K-mount lens. I know it doesn't shoot just wide open because it's in my hand. This leads me to believe I'm miss interpreting something about what a k-mount lens is. That is my first point of confusion. My 2nd point of confusion is... by 'only shoot wide open' does that mean if I get a 125 prime f4 that it will ALWAYS and ever be at f4, or does that mean it will only shoot at f4 if the camera tries to control it, or does that mean it will work the range of F stops if I mount it at a different aperture but never automatically stop down?
04-08-2010, 07:10 AM   #7
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All K mount lenses will work with the K20D. Most will work with stop-down metering using the green button. They are not limited to shooting wide open. A series lenses can be controlled by the camera, they just don't autofocus. I think Ira is starting to get Alzheimers.
04-08-2010, 07:11 AM   #8
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QuoteOriginally posted by smcook99 Quote
I apologize, I'm must be slow today, I'm having a hard time picking up on what you're saying about K-mount lenses.


You're saying that all K-mount lenses will work on my camera but only shoot wide open. So lets rule out all the M42 for a second and run with that. You said my k20d is a K-mount. I just got a Tamron 28-75 f2.8 which fits my k20d and so I assume it's a K-mount lens. I know it doesn't shoot just wide open because it's in my hand. This leads me to believe I'm miss interpreting something about what a k-mount lens is. That is my first point of confusion. My 2nd point of confusion is... by 'only shoot wide open' does that mean if I get a 125 prime f4 that it will ALWAYS and ever be at f4, or does that mean it will only shoot at f4 if the camera tries to control it, or does that mean it will work the range of F stops if I mount it at a different aperture but never automatically stop down?
No. K is just the mount.

The old fully manual lenses (both exposure and focusing) like the Pentax Takumars in K mount will only shoot at the lens's widest aperture (smallest number) when used on your sophisticated DSLR, but you have to use a manual metering method in conjunction with your green button to get the correct shutter speed. (It's easy to do.) The M42 screw Takumars, however, allow you to use all of your f stops.

Newer auto metering lenses in K mount (whether autofocusing or not, like the Pentax M series and later) will operate fine and give you full automatic metering functions, just like a brand-new lens.

04-08-2010, 07:12 AM   #9
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I think Ira was referring to the K-series lenses, not the K-mount. See Pentax Lens Review and Specification Database - Main Index for a list of all series (K, M, A, ..., DA).

//EDIT
OK, too late
04-08-2010, 07:13 AM   #10
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QuoteOriginally posted by boriscleto Quote
All K mount lenses will work with the K20D. Most will work with stop-down metering using the green button. They are not limited to shooting wide open. A series lenses can be controlled by the camera, they just don't autofocus. I think Ira is starting to get Alzheimers.
Huh??????/
04-08-2010, 07:13 AM   #11
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QuoteOriginally posted by sterretje Quote
I think Ira was referring to the K-series lenses, not the K-mount. See Pentax Lens Review and Specification Database - Main Index for a list of all series (K, M, A, ..., DA).

//EDIT
OK, too late
I'm just referring to the mount--not the series.

I guess I should have said PK.
04-08-2010, 07:14 AM   #12
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QuoteOriginally posted by Ira Quote
No. K is just the mount.
Newer auto metering lenses in K mount (whether autofocusing or not, like the Pentax M series and later) will operate fine and give you full automatic metering functions, just like a brand-new lens.
The M series has to be stop-down metered. Only the A series has auto-metering.
04-08-2010, 07:15 AM   #13
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So Cook, if you see a 30-year-old Vivitar lens in PK mount (Pentax K mount), that will only shoot wide open on your cam.
04-08-2010, 07:16 AM   #14
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QuoteOriginally posted by boriscleto Quote
The M series has to be stop-down metered. Only the A series has auto-metering.
Corrected.
04-08-2010, 07:24 AM   #15
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QuoteOriginally posted by Ira Quote
No. K is just the mount.

The old fully manual lenses (both exposure and focusing) like the Pentax Takumars in K mount will only shoot at the lens's widest aperture (smallest number) when used on your sophisticated DSLR, but you have to use a manual metering method in conjunction with your green button to get the correct shutter speed. (It's easy to do.) The M42 screw Takumars, however, allow you to use all of your f stops.

Newer auto metering lenses in K mount (whether autofocusing or not, like the Pentax M series and later) will operate fine and give you full automatic metering functions, just like a brand-new lens.
That is simply a mix-up. Depending on the camera, the old K-mount lenses (any lens of the pre A-generations, including the K and M series) will stop down for metering (Green Button) and also stop down to the chosen aperture during exposure, if you use the camera in M-mode. Only in the automatic exposure modes, the aperture is locked fully open.

Ben
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