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12-03-2017, 03:06 PM   #1
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Pentax k1 and with crop lenses

I got great information about using the 50mm DA F1.8 lens with the K1. Thanks for the info and the sample pics.

Does anyone have experiences using a the K1 with a DA 16-85mm lens and /or 10-20mm sigma lens?

Would love to know how they work in crop mode (how does it affect the megapixels/ image quality) and do they work in FF mode?

I currently use them with my K3. Thinking about upgrading to the k1 body but cant afford to buy new lenses at the moment.

Thanks in advance for the info.

12-03-2017, 03:16 PM   #2
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The 16-85mm only works in crop mode, so for a walkaround lens you'd want something with FF coverage, like the 24-70 or the 28-105mm. Not sure about the Sigma but it probably doesn't cover FF until later in the range.

In crop mode you get 15 megapixels, so quite a bit less resolution than the K-3. Other aspects of the image quality are unchanged.

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12-03-2017, 11:27 PM   #3
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I'm not sure which Sigma 10-20 you are talking about but I can comment on the Sigma Ex 10-20 f3.5:
* It has strong vignetting in FF from 10 - 14mm
* Vignetting wise its not bad from 15 - 20mm.
* In terms of IQ though the corners are pretty mushy and so I do not use mine in FF.
12-03-2017, 11:35 PM   #4

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Sigma 10-20 + 1.4x TC,its useable right thru the zoom range, corners are not sharp but they can be cropped out.

12-04-2017, 04:52 AM   #5
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There is at least one wide-angle Sigma zoom that is a DG (full frame) and another, very similar IIRC, that is DC (crop). So one must be careful.
12-05-2017, 12:23 PM   #6
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QuoteOriginally posted by pathdoc Quote
There is at least one wide-angle Sigma zoom that is a DG (full frame)
Yes, but that is not a 10-20, but a 12-24. This is the widest UW zoom lens out there for the K bayonet, there is but one UW prime that is even wider - the Irix 11mm.

For whatever dumb stupid reasons, Sigma has ceased manufacturing the 12-24 with Pentax mount, just about the time when the K-1 hit the market (thus being the perfect moment to make that lens interesting again, since it's a full-frame lens). If you're lucky, you can get a used copy. If you're really lucky, that used copy is in good condition.

The current incarnation, the "12-24mm F4 DG HSM Art" is not available in Pentax mount.
Only it's predecessors, the "12-24mm 4.5-5.6 II DG HSM" and the older "12-24mm 4.5-5.6 EX DG Asp IF" were produced with Pentax mount.

(And no, the Pentax SMC DA 12-24 is not a full frame lens, so it's no contender)
12-05-2017, 05:49 PM   #7
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QuoteOriginally posted by funktionsfrei Quote
Yes, but that is not a 10-20, but a 12-24. ...
(And no, the Pentax SMC DA 12-24 is not a full frame lens, so it's no contender)
I bought a refurbished Sigma 12-24 DG this year, Funktionsfrei ... it's not bad.

I also have the Pentax 12-24 and it's excellent. From 17mm on it works very well with the K-1 in full frame mode. For someone looking to go autofocus and less than 24 or 28mm, I'd recommend it, it's pretty good.

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