[wanderer2]

Starting not long after purchasing my K-1 3 + years ago I have slowly (because of financial restraints) been developing a lens kit of primes for landscape use. I finally have what I think will be everything I need from 20mm to 300mm. I'm now focusing on an extreme wide angle last because most of my landscape photography is in the mountains and I seldom need a lens even as wide as 20 mm. However, I do try to travel to the SE USA red rock country every year or two and shoot there, and I plan that again in 2020. And very occasionally I find a need for such a lens other places I wander and even here in Colorado.

So I'm looking for something about 15mm and need a rectilinear lens for full frame. I would prefer one with filter threads but if a filter adapter is available that should be suitable. I would prefer to avoid a fully manual lens but if that is the best choice otherwise would settle for that. My 20mm is a Pentax A lens, manual focusing but automatically sets exposure, and I'm ok with that. High image quality is essential and I do very large prints at times so I value sharpness. The great majority of my shooting is on a tripod so lens speed is not usually important.

Researching this in this Forum's lens review section and elsewhere, my short list of potential lenses is:
Irix 15mm
Samyang 14mm
Laowa 15mm
Pentax A 15mm

I realize none of these lenses have every feature I would desire and especially that the first three are all fully manual. I do find the Pentax A being partially automatic appealing but it's quite an old lens design and I wonder how it's performance compares to the three modern lenses?

Any suggestions and advice would be much appreciated. Am I missing anything worth considering other than the four named above? Does anyone have experience with how the Pentax A compares with the others (all of my current prime collection are Pentax and it would be nice, but not essential, do stay with Pentax)? Thanks for any help.

Mike

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Last edited by wanderer2; 11-20-2019 at 10:28 PM.

[Sandy Hancock]

Personally, I went for the DFA 15-30/2.8 zoom. More recently I extended my wide end with the (ridiculously wide, and ridiculously named) Laowa 12/2.8 D Dreamer Zero-D. I haven't used the latter much yet, but I'm very taken with its compactness and build quality.

For landscape use, the zoom is easily a match of my FA 20/2.8 and FA* 24/2.0 primes, with the added benefit of weather sealing. The Lee 150mm filter system works very well with it.

That said, I have only heard good reports from the Irix 15/2.4 lenses - that would my choice of prime in that range if I didn't already have the zoom.

[MaineNative]

I have the Samyang 14 and it has very good image quality. I usually use it for astrophotography, but I have used it for landscapes and wide-angle architectural shots. (I had to adjust the infinity stop when I got it, but fine since then.). I have the Haida 150mm filter holder for it, which does create some vignetting in the corners. The distortion isn’t too bad for an ultra-wide.

I rented the DFA 15-30. It is a great lens but for me it is very heavy to carry around. I have the DA 10-17 fisheye for my K-5. It is a fisheye on the short end, but it is lightweight with a 180-degree diagonal field of view and less distortion at 15-17 mm.

I ended up getting a used FA 20 for an auto-focus wide angle.

[beachboy2]

I bought the the Irix 15mm. no regrets. It's a great lens. MF is not an issue, probably an advantage. Set the focus. Lock if desired and concentrate on composure and verticals.

[KieranCoughlan]

I have the DA 10-17 fisheye for my K-5. It is a fisheye on the short end, but it is lightweight with a 180-degree diagonal field of view and less distortion at 15-17 mm

This is a very underrated lens, and yes agree at the 15-17 range the distortion is much less (easily corrected in post). As for the reviewers who criticised it for suffering from distortion...it's a fisheye...that's what it does🤓

[SteveinSLC]

It's not a cheap option, but the new DA* 11-18 works on my K-1 with no significant vignetting from 15-18. Not much of a range, but you get a Pentax * quality lens, autofocus, weatherproofing, and the ability to use threaded filters. It's not small, but it's smaller than the 15-30.

[photoptimist]

The Sigma 12-24 DG deserves some consideration, too. It is AF but does not support filters other than thin slip-ins behind the lens. It's very rectilinear and nicely sharp on the wide end.

I also have the Samyang/Rokinon 14/2.8 which is great for astro but does have a strange "mustache" distortion that some don't like for architectural shots.

[ramiot]

I bought the Rokinon 14mm for night photography /Astrophotography but must admit that it does a great job for landscape photographs. The only issue being that you cannot have CP or ND filters that would be nice in landscapr photography. here are a few samples... taken this automn in Mont Tremblant Park.

[blackcloudbrew]

I've used the DFA 15-30 mostly for the best range in wide angle landscape images. I also have the Venus Laowa 12mm f2.8. This lens, which is an excellent lens, is so wide that it's almost too wide on the K-1 at times. It's a quality option for a UWA, but I find it often too wide. The DFA 15-30 is much more versatile IMHO.

Here is a slot canyon with the 12mm.

another with the DFDA 15-30.

[Snapppy]

I own and use the Rokinon 14mm 2.8 on my Pentax K-1 and join with others in saying it's a keeper. The benefits are a low cost, so you can try it without much risk. Also relatively small and lightweight (the front element is large, but the overall form factor remains on the smaller side for an UW). One downside is it does not take filters, but there are adapters like this for it:
WonderPana Filter Holder for Rokinon/Samyang 14mm f/2.8 ED AS IF UMC L ? Fotodiox, Inc. USA

I have never used it, but seems expensive and then you need to use 145mm filters....

[cmohr]

The Sigma 12-24 DG deserves some consideration, too. It is AF but does not support filters other than thin slip-ins behind the lens. It's very rectilinear and nicely sharp on the wide end.

I also have the Samyang/Rokinon 14/2.8 which is great for astro but does have a strange "mustache" distortion that some don't like for architectural shots.

Another vote for the Sigma 12-24 here too, I used it for years on Film, used it on crop APS-c all these years until, I could use it again on my K-1.. It's wide, very wide. You can actually put a filter on the front, if you only remove the lens cap itself, and not the whole cap, but it will vignette when doing so.

There's also the Sigma 15-30 as well, I bought one just when the K-1 was coming out, and it's also very good, I only replaced it a year or so ago with the DFA 15-30, when I was left some "Coin" from an elderly relative, who knew I loved photography.

I also have the Sigma 14mm/2.8, AF yes, but mine sufferred the same as most I believe, the focus tightened up, AF could not work, and even the manual focus was stiff, actually this was kind of OK as when you set the focus, it stayed there, I liked it, but , it does have a lot of CA.

[DeadJohn]

...Irix 15mm
Samyang 14mm
Laowa 15mm
Pentax A 15mm...
I realize none of these lenses have every feature I would desire and especially that the first three are all fully manual.

The Samyang 14 has an A-setting. I used it with my K-5 and K-1 and it worked fine in Av mode.

I was happy with the Samyang. Strengths were sharpness and very little coma distortion. Color, contrast, and flare resistance were fair - not bad but not as good as the Pentax 15-30.

[bdery]

Irix 15mm
Samyang 14mm
Laowa 15mm
Pentax A 15mm

Why not the Laowa 12mm? It's my favourite of the lot (the Pentax 15-30 is slightly superior optically, but bigger and not as wide). To read my opinion on the Irix 15, see here.

[Digitalis]

There's also the Sigma 15-30 as well, I bought one just when the K-1 was coming out, and it's also very good

I had a copy of that lens, they aren't very common in K-mount. I sold my copy of it several years ago. I recall It had excellent resolving power @15mm - it performed very well at wide focal lengths on my optics bench. However the lens performed rather poorly @30mm at that focal length the lens lost a lot of contrast, and only just started to recover it @f/11. I also found that lens had significant flare issues. The SMCP-DFA* 15-30mm f/2.8 lens with its superior coatings was visibly superior, you could see the difference between them even in the thumbnail previews.

[barondla]

I have the Pentax A 15 and it does a decent job. I like it. Looking at images on this forum, newer lenses like the Pentax 15-30 will be sharper and more highly corrected. Depends on the rendition you like.

The lens won't accept filters directly. There are built in filters that aren't much use today. Think the choices are none, uv, skylight, red, and yellow. Good luck with your selection.
Thanks,
barondla