[Na Horuk]

FA31 is certainly excellent with APS-C but I believe it is not the top lens for high resolution FF sensor; it is enough to study the MTF figures. The FA31 was tested by Photozone at 10 Mpx and the center resolution at f/1.8 was 1848.5 lw/ph. Sigma A 35 as tested on an FF Nikon gave center resolution of 3262 lw/ph at f/1.4.

Ah, be careful with comparisons between cameras. You can't compare lens performance on different cameras. You can check the same lens tested on different cameras, and you will see that it gives different results on different cameras. It would be more fair to compare tests on D800E and K-1, but even that is not perfect because even though they have the same MP, they are not the exact same.
But I do agree that FA 31mm was not made for pure sharpness and optical correction - the Sigma 35mm was. Sigma is a super sharp lens. Though, lots of people don't need super resolution. They prefer rendering, bokeh, colours, contrasts, lots of things.. This is why some people don't like Sigma 35mm Art and Zeiss Otus 35mm as much. But yes, if you need pure sharpness, the Sigma 35mm is a good choice
That said, my DA 21mm is really sharp, but I fell in love with its contrasty rendering. I don't need it to be as sharp as the Sigma 35mm (which, full disclosure, I never owned, only read reviews and checked raw dng samples)

[leekil]

Ah, be careful with comparisons between cameras. You can't compare lens performance on different cameras. You can check the same lens tested on different cameras, and you will see that it gives different results on different cameras. It would be more fair to compare tests on D800E and K-1, but even that is not perfect because even though they have the same MP, they are not the exact same.
But I do agree that FA 31mm was not made for pure sharpness and optical correction - the Sigma 35mm was. Sigma is a super sharp lens. Though, lots of people don't need super resolution. They prefer rendering, bokeh, colours, contrasts, lots of things.. This is why some people don't like Sigma 35mm Art and Zeiss Otus 35mm as much. But yes, if you need pure sharpness, the Sigma 35mm is a good choice
That said, my DA 21mm is really sharp, but I fell in love with its contrasty rendering. I don't need it to be as sharp as the Sigma 35mm (which, full disclosure, I never owned, only read reviews and checked raw dng samples)

Independent of the variation between different but similar cameras, and the fact that the FA31 was not made for sharpness, there is such a vast difference between the specs being compared here, the "results" should be obviously useless. The FA31 numbers were on a K10D -- 10MP with an AA filter; the Sigma test used a 20MP Nikon D5 *without* an AA filter. Note that the FA31 was also tested on the K-5 by Photozone, with a significant increase in the resolution measured compared to the K10 test -- thought still with an AA filter. I've been impressed by the resolution of the FA31 in the past, and though I wouldn't be surprised at the 35 Art being higher due to the seeming focus on resolution by Sigma, the FA31 is still no slouch in that area, and I'm not sure we have a test that has really measured its limits.

[D1N0]

Photozone has tested the ART on the D7000 as well which has the same sensor as the K-5



FA 31 on K-5:



DA 35mm 2.4 on the K-5



Not so much worse is it?

[StefanMikes]

You imply that line per millimeters is the only element of interest in determining a lens's quality? Surely you don't mean that.

As Cartier-Bresson said, sharpness is a bourgeois concept.

I clearly say the parameters defining a top lens are its sharpness, lack of vignetting, lack of distortion, lack of CAs, colour rendition capability, and pleasant bokeh. Cartier-Bresson shoot black and white and certainly he could not use a modern, high resolution digital camera.

EDIT:
D1N0: I thought we were talking a full-frame sensor....



EDIT: It is hard to distinguish which photo was taken with which 35 mm lens on *APS-C*, save the bokeh circle (one is decidedly better than the other one - see it at the right hand side). The difference might be visible on FF, though, especially for corners and sides. Both pictures at f/2.8.

---

Last edited by StefanMikes; 06-29-2017 at 10:46 PM.

[D1N0]

D1N0: I thought we were talking a full-frame sensor....

Well you decided to compare the K10D (10mp) with the Nikon D3s FF 24mp to proclaim the Sigma is much sharper. Photozone hasn't tested any lenses on the K-1


Here a comparison of the sigma art on the 36mp D800e and the 10 mp D200. Sigma 35mm F1.4 DG HSM A Nikon on Nikon D800E vs Sigma 35mm F1.4 DG HSM A Nikon on Nikon D200


Which Sigma should I buy? The one on the D800e of course because the one on the D200 obviously is not very sharp.

[mikesbike]

Although I much agree with these views, let us bear in mind the fame of the FA31 originated in the times when none of Pentax-brand owners ever planned making an FF digital SLR. FA31 is certainly excellent with APS-C but I believe it is not the top lens for high resolution FF sensor; it is enough to study the MTF figures. The FA31 was tested by Photozone at 10 Mpx and the center resolution at f/1.8 was 1848.5 lw/ph. Sigma A 35 as tested on an FF Nikon gave center resolution of 3262 lw/ph at f/1.4. You don't need pixel-peeking to determine that: It is clearly visible in pictures taken.

Although certainly the FA31 is a respectable lens, its high price and the old design make the lens natural to be reused by existing owners on the K-1 body but I would think thrice before I recommended the FA31 to a new user. Why to pay twice what you spend for Sigma to buy a lens that is outresolved by the K-1 sensor? And well, a 6-degree angle of view difference between both lenses? Is it worth paying the double price? I doubt and that's why I chose the Sigma for my coming K-1 body though I could afford the Pentax Limited lens.

Tests such as Photozone have ratings in the poor through excellent categories. Some testing "excellent" are more "excellent" than others as far as resolution is concerned, but from what I've experienced, this is not usually noticeable for differences in sharpness in real-life prints. Unfortunately, the FA 31mm Ltd has not been tested using a full-frame, high-megapixel DSLR. It was NOT designed for APS-C use before Pentax came out with a FF model. It was designed for full-frame use with 35mm film before Pentax had any DSLR cameras.

I might pay twice the price to get what I want. What we are trying to do here is not recommend the FA 31mm Ltd to a new user, but attempt to duplicate a DA 21mm Ltd on an APS-C body for a user of that setup, on a FF body. So apropos to Sandy's comments, what kind of design is the DA 21mm Ltd and why? It is pricey for a prime having only an f/3.2 aperture- why? Because it is an exceptionally compact design having an exceptional build quality, and exceptional imaging qualities. So to do what we are trying to do, we have to mimic the characteristics of this camera/lens setup on a FF body as closely as possible. I do not have the FA 31mm Ltd, but I do have other Limited primes, both FA and DA models, including the DA 21mm, and I do know that a major attraction they offer is a combination of fine quality with compactness.

I do not have a K-1 but I can easily replicate what the difference would be like in terms of use- handling and shooting photos, between the Sigma 35mm A lens and the Pentax FA 31mm Ltd on a K-1 body. I have already done so many times. I've had the DA 21mm Ltd for about 6 years, and i've had a Sigma 24mm EX DG f/1.8 for much longer. On APS-C bodies, its framing is about the same as a 35mm lens would be on a FF body, and I do use it as such when I need what it has to offer. Now I can tell you that actually carrying and using this lens is a much different experience than having my DA 21mm Ltd on the camera. The difference between 24mm and 21mm does not seem like much, but framing with the DA 21mm is noticeably wider, more inclusive, and for contrast and overall image rendering, I prefer the results I get from it. When I need the faster aperture I am forced to resort to the Sigma 24mm. An FA 31mm Ltd on a FF body would yield even wider framing. Handling is far different because the Sigma lens is much larger and heavier. Although the FA 31mm Ltd is also larger and heavier than the DA 21mm, it is not nearly as large or heavy as the Sigma, and the ratio of lens compactness to camera body mass, while still not as compact, is still a fair comparison to the DA 21mm on a smaller APS-C metal-body DSLR. So for the Limited lens design objective of compact handling with high quality of build and optics, plus framing, the FA 31mm f/1.8 Ltd is about as close as we can come on the K-1 to what the DA 21mm f/3.2 delivers on a high-quality APS-C body.

[abruzzi]

Of course all this discussion of the Sigma 35mm art and the D FA 31 Limited, while very interesting, misses the following line from the OPs question:

Budget is restrained, arthritis limits weight ...

Neither is likely to meet the requirements of the first clause, and at least the Sigma probably probably doesn't meet the requirements of the second. Sigma does make a 30 f1.4 Art that is cheaper and smaller than the 35 Art, but I don't know if $500 is cheaper enough for the OP and doesn't seem to be found used very often. There is a predecessor 30 f1.4 EX DC that can be found for a bit over $200, but I'd probably rather have the the Pentax F28 or FA28.

EDIT: For comparison on weight:

DA 21 limited: 140g
F28: 180g
FA28: 185g
FA31 Limited: 345g

30 f1.4 EX DC HSM: 430g
30 f1.4 Art: 435g
35 f1.4 Art: 665g

---

Last edited by abruzzi; 06-30-2017 at 06:17 AM.

[pres589]

The Sigma 30's are not full frame compatible. They're also not small. Really not anything like the DA21 design or intent.

I agree with the F or FA28mm suggestions. Or the DA35 f2.4 which is quite light.

I keep wishing that a new F28 f2.8 with DC focus and some weather resistance would show up. Seems like the perfect answer to this sort of question.

[TER-OR]

What's wrong with the DA40 on the K1? It may be a bit tighter than the 21 on an ASPC, but it's still a pancake and can be found used for great prices. Since it is based on the old film version, it should work well on FF.

I have a Sigma 28mm f1.8 macro and it's really quite nice, but it's huge. The pancakes are just so much fun.
The older Sigma 30mm is worth considering. Sigma 30mm F1.4 EX DC Lens Reviews - Sigma Lenses - Pentax Lens Review Database

[abruzzi]

The Sigma 30's are not full frame compatible. They're also not small. Really not anything like the DA21 design or intent.

You're right, my mistake, thanks for correcting me. Nonetheless, I wasn't really recommending it, as I suspect the pentax 28 is the best option, if price and size are limiting factors. There is also an older Sigma 28 ƒ1.8 which does seem to be full frame. But its big (500g) and unless you need that 1 1/3 stops...

[Na Horuk]

Pentax is amazing when it comes to these super compact Limited lenses. DA 21mm, DA 40mm, DA 70mm... you can pack three high quality primes with amazing rendering into a small small bag, and you are set for most situations. Add a fast 50mm and maybe something a little wider (15mm) and you are set! It is too bad the DA 21mm is APSC and there is no direct equivalent for FF. I think Pentax will release another wide angle prime after the announced 50mm and 85mm. Something between 20 and 28mm, FF compatible, but we don't know when.
I don't want to keep repeating myself, but my vote goes to a good old 28mm (F, FA) and DA 40mm (can get the HD limited if you want to splurge, or just the XS if you want to go budget). Or an older manual focus 28mm (I recommend at least A series, so you have auto aperture). Or a Voigtlander - fairly compact, good quality rendering, people love these, but they are rare and hard to find.

The mentioned Sigma lenses are all fairly big, and the 30mm ones have some problems. The older one has triangular bokeh highlights, many of the new Sigma lenses have AF problems.. and they are all pretty big. Sigma is no longer the super cheap competitor, now their lenses aren't cheap as chips. And the final straw - OP wants something that renders like the DA 21mm. Sigma is making reputation for sharp lenses, but not for lenses with amazing colours and contrasts. I've seen some posts complaining about the general Sigma 'look' and expressing a preference for Pentax.
To each their own! Hope OP finds what they need

[mikesbike]

A have had the FA 28mm f/2.8 for many years, and used it for film shooting. It is a fine lens, got top test reviews. It certainly is a viable answer to the question of replicating the DA 21mm Ltd/APS-C body combo on a K-1. It is well-made though not the build quality of a Limited, but then even a perfect used one would not be all that costly. AF with mine is fast and accurate.

---------- Post added 06-30-17 at 11:45 AM ----------

Photozone has tested the ART on the D7000 as well which has the same sensor as the K-5



FA 31 on K-5:



DA 35mm 2.4 on the K-5



Not so much worse is it?

Thanks for this more valid comparison! It is true that comparing lens tests between different cameras can be misleading. One thing to keep in mind is such resolution tests do not translate accurately from an APS-C camera to a FF camera. The numbers given are lines per picture height. The picture height for FF is 24mm compared to 16mm for APS-C. So of course the lines are condensed in a smaller area with APS-C. You can have the same resolution as an APS-C body with a FF body test but having the additional 8mm of hight allows adding more lines to get a larger total number.

[zapp]

The discussion on Pentax 31 and Sigma 35 will go on forever. The only new lens that matches the DA21 is the D-FA24-70. Don't blame me for mentioning the zoom, but it is the only up to date lens here.
I liked to work with K5 and 21/40 combo - nice, small, fun - not availbale for K1. 35/85 combo would be nice. Overall sharpness and AF type is won by Sigma everything else is taste - and why should I tell someone to buy a 15 year old lens for a new digital camera. I had the 31 on APS-C and was not happy with the overall feel. Let's see what the D-FA 85 will be like besides huge and wait for the Pentax D-FA 35.

[Transit]

Thanks once again for the helpful guidance.
I have bought an F-28/2.8 from a chap on the marketplace.
now the question of which hood to get begins
Pete

[GUB]

Thanks once again for the helpful guidance.
I have bought an F-28/2.8 from a chap on the marketplace.
now the question of which hood to get begins
Pete

Hold fire on hoods Pete - I got 20 of these coming in a week or so - hopefully they will do the trick. Even the short round metal ones at Ali are too long for the 28s. Going to the K1 from the K01 has been a bit of an upset are far as hoods are concerned. Buy Products Online from China Wholesalers at Aliexpress.com
EDIT This link might work better https://www.aliexpress.com/item/49mm-Flower-Petal-sharped-Lens-Hood-for-Cano...323053467.html