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02-28-2013, 01:42 AM   #1
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Widest and fastest K Mount lens?

Can anyone tell me what the widest and fastest lens for the K mount system is? Ive seen the Sigma 10-20mm at F3.5, but ideally id like, say a 14mm F2.8 but it seems no such lens exists for Pentax. Theres the Pentax Limited 15mm but its F4. I have a Pentax M 28mm F2.8, but id like something even wider.

Any suggestions?

EDIT: Sorry, i have seen the Rokinon 14mm F2.8 and the Samyang 14mm f2.8. Are these considered fish eye? And is this as wide as it gets for Pentax?


Last edited by curlednoodles; 02-28-2013 at 01:55 AM.
02-28-2013, 01:55 AM   #2
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QuoteOriginally posted by curlednoodles Quote
Can anyone tell me what the widest and fastest lens for the K mount system is? Ive seen the Sigma 10-20mm at F3.5, but ideally id like, say a 14mm F2.8 but it seems no such lens exists for Pentax. Theres the Pentax Limited 15mm but its F4. I have a Pentax M 28mm F2.8, but id like something even wider.

Any suggestions?

EDIT: Sorry, i have seen the Rokinon 14mm F2.8 and the Samyang 14mm f2.8. Are these considered fish eye? And is this as wide as it gets for Pentax?
I have Tamron 17-50 constant f 2.8, nice lens.
02-28-2013, 01:57 AM   #3
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QuoteOriginally posted by curlednoodles Quote
ideally id like, say a 14mm F2.8
Samyang 14mm F2.8 ED AS IF UMC Lens Reviews - Samyang Lenses - Pentax Lens Review Database

Can't wait for mine to arrive. Just shipped a few hours ago from Hong Kong .

Edit for your edit, no, have a look at the forums or lens reviews for down to 8mm (Samyang again). Personally I'd rather rectilinear. Although I tend to alter the projection ("distortion") in software anyway.

Last edited by russell2pi; 02-28-2013 at 02:03 AM.
02-28-2013, 02:06 AM   #4
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There is a Pentax DA14mm f2.8 available

This is the reference page at B&H Photo for the wide angles in K-mount. Prime lenses
SLR Lenses| B&H Photo Video

Bower/Samyang/Rokinon are manual focus
The 2 Sigmas and the Pentaxes are AF


Of the discontinued glass which are rarer (more expensive) and larger due to full frame compatibility.
FA20mm f2.8
FA*24mm f2

the only one wider is the A15mm f3.5 which is manual focus, ultra rare and expensive


You have to remember that the 14mm on you digital is the same field of view on a 21mm on film. They just didnt make that many wider lenses like 10 or 15mm back then.

02-28-2013, 02:06 AM   #5
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What about the Pentax DA 14mm f2.8?
Pentax Super Wide Angle SMCP-DA 14mm f/2.8 Autofocus Lens 21510
02-28-2013, 02:21 AM   #6
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Wow thanks for the replies. The Rokinon/samyang is looking good. I have a K30 so manual focus is not a concern, plus it will be used on a tripod. Im looking to take some night shots, which is why id like the F2.8. I had considered the Sigma 10-20mm but at F3.5 i dont think its fast enough for star shots and the like?
02-28-2013, 02:27 AM   #7
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QuoteOriginally posted by curlednoodles Quote
I had considered the Sigma 10-20mm but at F3.5 i dont think its fast enough for star shots and the like?
Only 2/3 of a stop difference - how much more noise does 2/3 stop of ISO change bring? Not much. Other factors like IQ, price and versatility would play more of a role for me.
02-28-2013, 02:32 AM   #8
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QuoteOriginally posted by curlednoodles Quote
manual focus is not a concern, plus it will be used on a tripod
Remember also that the depth of field i.e. apparently in focus, is massive with these ultra wide angle lenses. So they are just a joy to use, as I've said elsewhere in this forum "Currently having an illicit affair with my SMC Pentax-A 15mm F3.5".

02-28-2013, 02:40 AM   #9
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My sigma 10mm f2.8 fisheye is fast. It's a big heavy lump. Sigma also makes a wider circular fisheye which I think is also 2.8.
02-28-2013, 03:00 AM   #10
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QuoteOriginally posted by Zav Quote
It exists, is expensive, and I have a copy - but I am a little disappointed by the IQ, which seems "softer" somehow, than other wides that I have, notably softer than the Pentax 10-17 at "roughly 14mm".

Maybe I need to take it out and use it until I learn where its sweet spots are.
02-28-2013, 05:44 AM   #11
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QuoteOriginally posted by curlednoodles Quote
Wow thanks for the replies. The Rokinon/samyang is looking good. I have a K30 so manual focus is not a concern, plus it will be used on a tripod. Im looking to take some night shots, which is why id like the F2.8. I had considered the Sigma 10-20mm but at F3.5 i dont think its fast enough for star shots and the like?
I'm a beginner and your comments have confused what I thought I understood, so hopefully you can answer this for my own learning... Why do you need a fast lens for this? I thought that for doing landscape type stuff you generally use a smaller aperture to get greater depth of field. And as stars don't move much I'd have thought a slower lens would be fine along with a tripod. Have I got it all wrong?

Sorry to hijack it a little but you seem to have got the answers you wanted so hopefully you don't mind too much...
02-28-2013, 06:07 AM - 2 Likes   #12
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QuoteOriginally posted by thechumpen Quote
as stars don't move much
They move up to 360 degrees per day, i.e. 1/240 degrees per second. Might not sound like much but one pixel on a K5 with a 14mm lens is around 1/60 degree so that gives you theoretically 4 seconds of exposure before their motion becomes noticeable when pixel peeping. 4 seconds isn't very long for a night exposure - the bigger the aperture and the higher the ISO, the better.
02-28-2013, 06:26 AM - 1 Like   #13
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Hubble telescope, but you need a K-mount adapter!

02-28-2013, 06:30 AM   #14
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Very interesting, great explanation. That must be some serious pixel peeping Thanks...
02-28-2013, 06:52 AM   #15
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I have Sigma's 28mm f1.8 macro lens (works as f1.7 on some).
Great lens, not small nor particularly wide-angle, but very nice.
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