[JimJohnson]

Thanks. Nice images ! I'm more concerned with the wider end. The overwhelming majority of pics I took with my Sigma 10-20 on APS-C were at 10mm - about 2/3. The remaining third at 20mm. Very few in between. I would prefer rectilinear to fisheye, though.

I struggled with the same thing; although, with my Sigma 10-20 DC on my K-3, I subjectively shoot a lot around 12-15mm. The rectilinear ultrawide lens offerings for full-frame are both sparse and pricey. Based on availability and budget, I purchased a used FA 20-30 for my K-1 - - I paid a premium price for a pristine unit with the Pentax hood - and that cost me less than buying one of the several available without a hood and buying a replacement hood - - everybody I found wanted US$90 for $1 worth of injection molded plastic. I know at times I'll wish I had a 15mm lens, but decided being stubborn about it I would miss a lot of good shots at 20mm. I already had two options for 28mm (an A prime and DFA zoom)

[pinholecam]

Voigtlander 20/3.5 and Pentax M20/4 , FA20-35/4

The old 17mm lenses from various lenses can take screw on filters as well, but I don't like the edge IQ (stopped down ); A cheap Samyang 14/2.8 beats them for IQ.

[madbrain]

Voigtlander 20/3.5 and Pentax M20/4

These are both manual-focus, so off-topic here.

FA20-35/4

This one has already been mentioned.

A cheap Samyang 14/2.8 beats them for IQ.

Unfortunately, also MF.

---------- Post added 05-26-21 at 09:31 PM ----------

I've got one, it's not bad.

Oh, you do ? Would you mind reviewing it here on Pentaxforums ? You would be the first to do so.

Sigma 12-24mm F/4.5-5.6 DG HSM II Lens Reviews - Sigma Lenses - Pentax Lens Review Database

The non-HSM version has been reviewed.

Sigma 12-24mm F4.5-5.6 EX DG Aspherical Lens Reviews - Sigma Lenses - Pentax Lens Review Database

Oh, a CPL? I hope you won't be shooting outdoors with the sky in the shot?

Why not ?

[clackers]

The non-HSM version has been reviewed.

Ah, that's my version.

Are you sure the HSM version was ever released in K mount? I've never seen one.

Why not ?

Beginners mistake. Because the sky is uneven with the amount of light at certain angles, putting a CPL makes ugly uneven patches in the picture that are too difficult to postprocess out, IMHO.

An example from F-Stoppers: https://fstoppers.com/education/lessons-shooting-landscapes-my-first-ultra-wide-lens-257408

[fs999]

Ian is right, I bought the expensive Irix CPL and I don't use it anymore. Now I darken the blue and cyan colours.

Irix 15mm F2.4 with CPL


without CPL

[madbrain]

Ah, that's my version.

Are you sure the HSM version was ever released in K mount? I've never seen one.

Apparently, one has been made . Unless it's an error in the listing. But at $799 I think it has to be the HSM II version.

42nd Street Photo - Sigma 204109 - 12-24mm - Sigma Lenses For Pentax Mount - f/4.5-5.6 EX DG ASP HSM II Lens For Pentax

Beginners mistake. Because the sky is uneven with the amount of light at certain angles, putting a CPL makes ugly uneven patches in the picture that are too difficult to postprocess out, IMHO.

An example from F-Stoppers: Lessons From Shooting Landscapes With My First Ultra-Wide Lens | Fstoppers

Yes, I would agree that doesn't look right. But you can turn the CPL. Or, of course, remove it when inappropriate. I will dig some samples made with my K200D and 10-20 with CPL. I don't recall skies looking like that. Darker for sure, but not so unevenly. And I was shooting in JPEG, practically zero post processing in those days.
I have printed many such images.

Images taken from a Nikon compact by my husband the same day, often of the same subject, but without CPL looked positively bland in comparison. Of course, not only because of the lack of CPL, but the hazy skies really detracted from images.

---------- Post added 05-27-21 at 02:27 AM ----------

Ian is right, I bought the expensive Irix CPL and I don't use it anymore. Now I darken the blue and cyan colours.

Irix 15mm F2.4 with CPL


without CPL

In this example the CPL image doesn't look quite as bad as the fstoppers example. Your 2 images appear to be of different subjects, so hard to compare. I don't always want to use a polarizer, but on a wide angle it's something I want.

[UncleVanya]

Using a polarizer on extreme wide angle shots is a well known effect that some like but most don’t due to the uneven skies. Turn all you want, The sky is so wide in these types of shots the light is not going to polarize right. With the older linear polarizer (and perhaps the circular ones) you could use them for crude navigation by looking for the darkest patch of sky - which in the northern hemisphere was supposed to be north. This article suggests that Vikings used a similar technique for navigation:

Did Vikings navigate by polarized light? - Scientific American

Additionally excluding manual focus lenses is a bit odd given the extreme depth of field that lenses like these have. On the Sony Full Frame platform many of the most respected extreme wide angle lenses are manual focus primes. In effect you are narrowing your choices for very little gain of function. With a zoom perhaps this is more important as the longer end might be used more with faster moving objects.

[fs999]

In this example the CPL image doesn't look quite as bad as the fstoppers example. Your 2 images appear to be of different subjects, so hard to compare. I don't always want to use a polarizer, but on a wide angle it's something I want.

It's same pond on different times, but I have tried to minimize the dark part of the sky.
Wide angle is not ultra wide angle. Even on my Soligor 20mm I had that effect, it is because your are seeing a large part of the sky, larger than the dark sky effect of the CPL.
On 24 or 35 mm lenses the effect is not so much visible.

[jatrax]

As others have said using a polarizer on ultra-wide is often a bad idea. Yes, sometimes the blotchy effect isn't noticeable but usually it is. I have several hundred completely awful photos from the inside of Crater Lake that were ruined because of a polarizer. That was with the DA 12-24 and I thought I was being careful. So a hike all the way to the water inside the crater and the boat ride and I got mostly zip because of the polarizer.

There are uses for polarizers but personally I won't use one on anything wider than maybe 30mm on full frame. Any effect the polarizer will give you on the sky can be done better in post. Now if you are shooting waterfalls with no sky, that's a different thing.

I wonder if you are limiting yourself in lens choice by requiring filter threads when they might not be used as much as you think.

[clackers]

Unless it's an error in the listing. But at $799 I think it has to be the HSM II version.

42nd Street Photo - Sigma 204109 - 12-24mm - Sigma Lenses For Pentax Mount - f/4.5-5.6 EX DG ASP HSM II Lens For Pentax

I think that's an error, Madbrain.

I bet if you tried to purchase that, you'd be rung up or emailed and some apologetic sales rep would say it doesn't exist.

If you go to the Sigma website, you can look up their discontinued lenses, and their page for this one does not say K mount:

12-24mm F4.5-5.6 II DG HSM | View Discontinued Lenses | Lenses | SIGMA Corporation

I actually bought my Mk I online from Sigma America, it was a refurbished item. Whatever that means. The box and everything in it looked untouched, as if the box came straight off a warehouse shelf new.

[madbrain]

I think that's an error, Madbrain.

I bet if you tried to purchase that, you'd be rung up or emailed and some apologetic sales rep would say it doesn't exist.

If you go to the Sigma website, you can look up their discontinued lenses, and their page for this one does not say K mount:

12-24mm F4.5-5.6 II DG HSM | View Discontinued Lenses | Lenses | SIGMA Corporation

I actually bought my Mk I online from Sigma America, it was a refurbished item. Whatever that means. The box and everything in it looked untouched, as if the box came straight off a warehouse shelf new.

Quite possible you are right.

B&H also lists it as discontinued in HSM II version, Pentax mount, FYI.

https://www.bhphotovideo.com/c/product/755361-REG/Sigma_204109_12_24mm_F4_5_...981& . Same Sigma part number as 42nd St photo lists, 204109 .

So does Adorama at

https://www.adorama.com/sg12242pxafa.html?
This one lists part number 204109A .

So does Amazon.es :

Sigma 12-24mm F4,5-5, 6 DG HSM II Lente de Pentax (82mm Rosca de Filtro): Amazon.es: Electrónica

Maybe it had a very small production run ?

I don't think the HSM vs non-HSM matters all that much for me. Would rather pay a cheap price for the non-HSM version than $799 for the HSM.
The question of cost of filter system + CPL remains, though .

The current Sigma 12-24 ART doesn't exist for Pentax, but costs $1600 anyway, so would be a bit too rich for my taste.

B&H replied this about the Vu filters :

That filter holder ring would need other parts to work with a filter holder.
The actual VU filter holder is not available on our Web site.
It would be better to get a filter adapter kit like this one :that comes with a polarizing filter:

https://www.bhphotovideo.com/c/product/1360817-REG/fotodiox_wndpn186_esntlcp...981&

This kit comes with a polarizer, but it says it is for the 12-24mm F4 version .

That filter holder+CPL is for the Sigma ART 12-24. And $319 . Not for the older Sigma 12-24 DG or DG HSM II.

---------- Post added 05-27-21 at 06:12 PM ----------

BTW, I emailed 42nd st photo about the Sigma 12-24 HSM II yesterday, asking if they would discount it further, given that Sigma has dropped all Pentax support, and there would be effectively no warranty if anything went wrong with it during the warranty period. No response.
Maybe I'll call them tomorrow.

[madbrain]

Re: the CPL discussion on ultrawide, here are some shots I made with the Sigma 10-20 f4.5 with CPL. I was very much a "noob", had my K200D for less than 30 days at the time, and was shooting JPEG only. No PP.
I still love these shots today. It may not be to everyone's liking. But I know I would much rather have the CPL than not for these shots. When I went inside the castle, I did take the polarizer off. It loses about 2 stops of light, and the K200D only maxed at 1600 ISO, and you really didn't want to use that ISO on that camera, ever. Even 800 was pushing it. These are SOOC JPEGs. All taken at 10mm.

First one. The horizon has a lighter sky color. But there is no big dark patch as in the fstoppers example. The sky gradient color looks very nice to me. And I know without it, the picture would be much worse.


In the following, I think the CPL did its job nicely, except for the vignetting. Would not have wanted to be without the CPL.



In this one the sky is quite dark, but not too uneven. This is the result of wrong exposure. The K200D had a tendency to seriously underexpose, compared to current bodies. This can be compensated in post, even on a JPEG, but this is SOOC.
I actually like the gradient of the sky from top to bottom (horizon). There is no big dark patch in the sky. The worst thing I can say here is the vignetting from the filter.



In the following shot, I will admit sky looks somewhat patchy. It hadn't bothered me until this thread. Not quite sure how/if this can be helped in post or not on a JPEG. I only use Lightroom classic for PP, but none here.

[zjacreman]

It's not super easy to come by but the Tamron 17-35 F2.8-4 (Tamron SP AF 17-35mm F/2.8-4 Di LD Aspherical [IF] Lens Reviews - Tamron Lenses - Pentax Lens Review Database) takes 77mm filters.

[mikesbike]

I've had my Tokina AF 20-35mm f/3.5-4.5 (series II with a 77mm filter thread) for over 20 years, and have been again enjoying it on my K-1 II. It was tested by Pop Photo with a very high rating, and the 20mm end as being actually 19mm. Build quality is excellent.

---------- Post added 05-27-21 at 08:56 PM ----------

Tokina 19-35 is FF and takes screw in filters and the hood doesn't rotate with focus. I have used it on the K1 and didn't notice any vignette but I might not be as critical.
There is also a Cosina version but I have no experience with it

This one came later and was less expensive with a plastic body, but still well-made. It also has a 77mm filter thread and also received a very good review from Pop Photo. A used one in fine shape should be very inexpensive.

[jatrax]

I still love these shots today. It may not be to everyone's liking. But I know I would much rather have the CPL than not for these shots.

That's fine, in many cases a polarizer does do wonders. But in many other situations in produces horrible results with an ultra-wide. In your examples the effect is not very noticeable and you got some wonderful shots. it doesn't always work that way and I'm sure all anyone here wants is to make sure you are aware of the potential pitfalls. And be warned not to pull a stupid stunt like I need and shoot all day without really checking the results.