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SMC Pentax-FA 31mm F1.8 AL Limited

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85 324,354 Fri August 2, 2019
Recommended By Average Price Average User Rating
95% of reviewers $876.11 9.51
SMC Pentax-FA 31mm F1.8 AL Limited

SMC Pentax-FA 31mm F1.8 AL Limited
SMC Pentax-FA 31mm F1.8 AL Limited
SMC Pentax-FA 31mm F1.8 AL Limited

This Limited lens features all-metal barrel and a built-in hood. It is known for delivering exceptional wide-angle image quality.

SMC Pentax-FA 31mm F1.8 AL Limited
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (A setting)
Automatic, 9 blades
9 elements, 7 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
AF (screwdrive)
Min. Focus
30 cm
Max. Magnification
Filter Size
58 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 50 ° / 42 °
Full frame: 70 ° / 60 °
Dedicated pouch
Lens Cap
Dedicated metal push-on
Weather Sealing
Other Features
Diam x Length
65 x 68.5 mm (2.6 x 2.7 in.)
345 g (12.2 oz.)
Production Years
2001 to present (in production)
$896 USD current price
$880 USD at launch
Engraved Name
smc PENTAX-FA 1:1.8 31mm AL Limited
Product Code
20280 (silver), 20290 (black)
User reviews
In-depth review
One aspherical element, one ED element, one high refraction low dispertion element.

Black and silver

Screwdrive AutofocusBuilt-in HoodAperture RingAutomatic ApertureFull-Frame Support
Purchase: Buy the SMC Pentax-FA 31mm F1.8 AL Limited
In-Depth Review: Read our SMC Pentax-FA 31mm F1.8 AL Limited in-depth review!
Sample Photos: View Sample Photos

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Junior Member

Registered: May, 2011
Location: Melbourne
Posts: 29

27 users found this helpful
Lens Review Date: May 13, 2012 I can recommend this lens: No | Price: $690.00 | Rating: 3 

Pros: Build quality, colours
Cons: Aberrations, sharpness, price
Sharpness: 5    Aberrations: 5    Bokeh: 7    Autofocus: 6    Handling: 6    Value: 1    New or Used: Used    Camera Used: XR-3000, K-r, K-5,   

I've been using this lens in all kinds of conditions for all kinds of purposes; nightclubs, events, street, landscapes, and portraits. I can confidently say that I now know this lens well enough to give an informative review on all aspects of this lens in various demanding conditions. I will not 'go easy' on this lens because I like it, or give a 'feel good' review, because they are worthless. Instead, the ratings of 5-6 are underlined by 'Good', so I will use the pentax forums scale appropriately. Because of its high price and great reputation, I will judge it with an absolute comparison with all the standard primes that I've owned or used extensively, including the samyang 35/1.4, nikon 35/1.8G, nikon 50/1.8D and 50/1.8G (full frame), pentax 35/2.8 limited, sigma 30/1.4 (both nikon and pentax). Only afterwards will I factor cost and system into it.

I bought this lens, along with the sigma 30/1.4, off an acquaintance by paying 'rent' on it, with the rent paid being subtracted from the final purchasing price. This was great for me because I could use it while accumulating funds to pay it off, while being able to compare it to the sigma. A few months into my ownership I came upon a 35/2.8 macro and bought it, which has pushed me towards writing a review as I'd owned the three most expensive normal lenses for the pentax system.

Sharpness: I'm no pixel peeper, but high quality wide aperture primes should be able to be used wide open with a useful resolution, which is one of the reasons that people love them so much. Therefore I was disappointed when I checked the pictures at 50% and found that the 31/1.8 was comparable to the 50/1.8D and perhaps worse 35/1.8G. They're from different systems, but they show similar characteristics; moderately soft, low contrast, purple fringing and some chromatic aberration. I burrowed another 31/1.8 with great effort to make sure that it wasn't defective and got the same result. Then I viewed pictures from this lens online and I'd be clutching at straws to find an excuse for it.
Once stopped down to 4-5.6, this lens became very, very sharp, however nearly all prime lenses are expected to behave this way, and high end, modern zooms show excellent sharpness as well. My rating for sharpness is weighted for performance at wide apertures, as they do not require pixel peeping to check for sharpness, whereas the difference between very sharp and insanely sharp is much less important.

Aberrations: The performance in this area makes it obvious that this lens was not designed well for a digital sensor. Purple fringing and CAs are worse compared to the sigma 30/1.4, both wide open, which shows the advantage of modern technology even at a wider aperture.

Bokeh: Pretty good. This tends to be quite subjective but I found it similar to the sigma, slightly better than the nikon 35/1.8G, slightly worse than the samyang.

Autofocus: Loud but quite fast. The higher pitch is very 'catchy' and not suitable for quiet environments. If it were quieter and lower in pitch I would like it more, and even more so if it used a silent motor.

Handling: Being all metal, this lens feels durable and solid but becomes very nasty in cold weather, conducting heat away from my hands quickly. In weather where gloves are almost, but not quite necessary, this lens becomes a pain to touch.The compulsory hood is annoying and not fully useful, as it's made for a 31mm field of view. This is the same mistake as the 35/1.8G, but at least that one is removable.

Value/Practical recommendation: No sugar coating here. 1 is 'Poor'. If this lens did something unique, there would be a case for it. You could say that this is the only lens for pentax that goes up to f/1.8 while gaining great border sharpness when stopped down, but that looks more like a weakness of the pentax system than a strength of the 31/1.8. To put it into perspective, for $2000 you can get a K-5 + 31/1.8 or D700+50/1.8G. For $1400 you can get a D7000 and 35/1.8G. The sigma is sharper, and more importantly, has more contrast wide open while the 35/2.8 limited has comparable border sharpness from 4-5.6. For the price of this, you can get both of them. My advice is to stop pixel peeping at the borders and buy the sigma 30/1.4, but that may not be possible for some.
A fast standard prime with average performance should not cost this much. Despite this, it is the only option that exists, and some people will be forced into it if they NEED this specific combination.

There's no doubt that I'll attract haters for this review, but since when has a 10/10 'excellent' review helped anyone make a decision? Its reputation has painted it out to be something with no flaws, but the reality is that it is just another standard prime with a very high price tag.
Site Supporter

Registered: December, 2013
Location: Houston, TX
Posts: 1,717

10 users found this helpful
Lens Review Date: April 22, 2017 I can recommend this lens: Yes | Price: $1,000.00 | Rating: N/A 

Pros: Absolutely Stellar on APS-C
Cons: Middling on FF, high price, built-in hood
New or Used: New    Camera Used: K-5 IIs and K-1   

I've avoided giving numerical scores in the above listings because the number depends entirely on whether you use this lens with an APS-C or the full frame K-1. It's a very different story with the two sensor sizes.

My usage heavily colors the direction my review takes. I shoot people almost exclusively with a little bit of travel sites when I do that. I prize rendering and use a lot of focus points off center because I don't position my models in the middle. I push my equipment to the edge of its capabilities and expect a lot of it. I figure if you're considering a $1000 lens, you probably have high expectations too!

APS-C Sharpness: 10
Full Frame Sharpness: 7
On APS-C, this is probably the best lens you could use. It's sharp and it has a very distinct means of rendering textures that give it a characteristic look. It has superlative 3D pop: it's sharp in the focal plane and smooth and smarmy outside with a quick drop. It's gorgeous, in a word. There was a reason why this lens rarely came off my K-5IIs. Contrast is strong.

On Full Frame, it's a different story. This lens doesn't pack a lot of resolution and it renders things kinda...dull. The contrast is much weaker and it just looks...kinda meh. It's not terrible and some post-processing sharpening helps but this lens is sadly not up to snuff for the K-1. I look forward to the modern replacement on the roadmap.

APS-C Aberrations: 8.5
Full Frame Aberrations: 6
In high contrast situations, this lens has a propensity to purple fringing, although it's not nearly as bad as the FA77, which I would describe as "fringing like crazy." It's usually easy correctable in post processing, however. Green-bokeh fringing is quite pronounced, more than any lens I've ever seen, and not fixable. If you're a purist, it's an issue, but I'd say it's part of the lens's character. I wouldn't call it unpleasing but it's very noticeable if you look for such things.

On an APS-C camera, barrel distortion is well controlled and the lens is sharp from corner-to-corner. On a full-frame camera, this is not the case and the lens displays significant distortion toward the edge of the frame. In particular, faces tend to be warped badly and geometries distorted. The center is great, however, which is why this lens excels on an APS-C camera.

It should be noted that wide open, this lens is not so good. You really need to stop down to f/2.5 or so to see it shine. f/2.8 is spectacular, at least as APS-C goes.

APS-C Bokeh: 9
Full Frame Bokeh: 7
I've knocked the APS-C bokeh down to a 9 because of the ubiquity of green fringing. Otherwise, it's smooth, clear, and really really pleasing. I found myself in awe of what this lens could do on my APS-C. Maybe I was just inexperienced but it's just amazing.

On the K-1,'s more complicated. Because you need to be closer to get the same framing as you would on APS-C, you run into issues with perspective distortion with certain subjects, such as humans. As a result, you need to move farther back...but the short focal length means you lose a lot of your background blur in the process. I've rated this a 7 because while the quality is the same, it's much harder to obtain it: you don't want to be close to your subject so you are forced to back up and open up the lens. Then the focus accuracy decreases's just not so fun. Maybe I'm just too used to using it as I did with APS-C and disappointed that I cannot.

Never had a problem with my first copy on APS-C. I damaged the lens after getting my K-1 and had a host of issues. I had it repaired and found the focus erratic. I replaced the lens with a new copy and sent that one back because it's focus was erratic. The new one hasn't arrived yet. I'm worried this lens itself and the K-1 just don't get along well. I've found it really has issues with the K-1 in difficult contrast situations. In particular, if you're using the outer focus points with the's a crapshoot. This makes sense: the focus points on the K-1 are much farther from the center of the frame than the outer focus points on an APS-C body. As I've described the distortion and contrast issues as the larger image circle is used, this explains the focus issues.

Remember that this lens was designed for a film body like the MZ-S, which had a state of the art 6 focus points, all of which are in the center. The lens really struggles with off-center focus points on a full-frame camera in a way it did not with an APS-C body.

Handling: 8
The lens is small and compact, although it's larger than other APS-C lenses you might acquire. It's modest for a full frame lens. I knocked this down some points because the built-in hood is irritating. It's completely insufficient on APS-C to the point of uselessness; it impedes the use of another hood simply because it gets in the way. Fortunately, a metal screw-in hood meant for a Panasonic camera can be had for a few dollars and it works perfectly (search the forums for it) but this hood vignettes on full frame badly. On FF, you're stuck with the built-in one because you can't add anything that protrudes from the sides, so a short rubber hood won't work. Another major downside is that only the Hoya variable ND filter will fit in side and that filter doesn't have threads on the outside, so you have to remove the add-on hood if you're using it on APS-C.

Aside from the hood issues, though, the lens is great in its ergonomics. It's small and well-balanced on every camera.

APS-C Value: 8
Full Frame Value: 5
This lens is pricey and that doesn't depend on the body. But what you get on an APS-C body is a premium normal-FoV lens and on full frame, you have a very overpriced middle-class wide-angle lens. I haven't used the FA35 but I suspect the FA31 isn't light years better than it on FF, at least not worth 3-4x the price. And that's what hurts this lens's value: it's an ok lens but it's not $1000 good on full frame. It is on on APS-C, where it is the alpha, the omega, and everything else between for crop bodies.

While full-frame compatible, I can't really recommend the lens for the K-1 simply because of it's price. It's a modest performer and the truth is we're stuck with it: there's nothing else available in this focal length except the FA35. There are other options for APS-C (like the DA35 Macro) but the FA31 beats them hands down. It should be your go-to lens on APS-C and one you use occasionally on the K-1. I've personally come to prefer the FA*24, which is not as sharp, of course, but has more interesting rendering that makes up for it.

What else? Oh, color. It's quite nice and if this is all you know, you'd be quite pleased with it. However, it's definitely not as accurate or punchy as either the FA77 or DA*55, both of which boast superlative color saturation. This lens seems to do best in bright sunlight with landscapes; I find it a bit ruddy inside or without 50-60% flash to ambient ratio.
Forum Member

Registered: September, 2009
Location: Kyoto
Posts: 72

9 users found this helpful
Lens Review Date: October 13, 2012 I can recommend this lens: No | Price: $700.00 | Rating: 10 

Pros: Kills LBA dead.
Cons: Diminishing returns.
Sharpness: 10    Aberrations: 10    Bokeh: 10    Autofocus: 10    Handling: 10    Value: 10    New or Used: Used    Camera Used: K10D   

Let's get it out of the way now: if you feel that this lens offers poor value for money, go ahead and buy one of the other Pentax primes instead. If you'll accept my recommendation, I suggest the DA 35mm F2.8 macro as the best performance for your dollar, and be sure to consider the FA35/2 and DA35/2.4 also.

The FA31 is not of that material world of measurements and money. She (for it is so) is the prima donna of the Pentax lens catalog. The best lens Pentax ever made, and arguably the best lens from any of the major SLR companies. Yes, better than the Distagon T* 35/2 ZF/ZK, if you insist on knowing how it stacks up against the clearest competitor.

But, please, that would be like trying to score Placido Domingo on points against Maria Callas. Really, a pointless waste of effort, and frankly a disservice to both singers and the art in general.

To see the attraction of the FA31, you have to be able to feel the rush, the wonder, in obtaining a lens that combines a 31mm (47mm eff APSC) field of view with the discipline, smoothness, and depth of a medium telephoto portrait lens. Essentially, it turns your APSC dSLR into a 6x7. If you don't see how fabulous that might be, great, take the blue pill, buy the DA35 on your way out. I'm just trying to convey my thoughts. No evangelism from me.

I do not think buying the FA31 is a good idea for most people. Those who do may be disappointed, and will be, thinking that for the price paid they deserve clinical perfection.

Still I remember the first day I went out with the lens on the front of my K10D (excellent pairing as far as handling goes, by the way). I took some photos of my daughter in a restaurant, just off-the-cuff kind of stuff, fooling around. I was floored by the results. Just plain gorgeous. Stunningly deep color, superb skin tones, and a confident, masterly rendering of the background blur.

Several years later, I'm still just as much in love with my FA31 as I was that first day, more so even.

Marriage? That pretty much describes it, yes.
Veteran Member

Registered: June, 2012
Location: Boise Idaho
Posts: 466

8 users found this helpful
Lens Review Date: January 6, 2015 I can recommend this lens: Yes | Price: $850.00 | Rating: 9 

Pros: Contrast, Color, Resolution, Metal Construction, Perfect FOV, Manual Aperture Ring,
Cons: Permanent Hood (no filters), Price (understandable)
Sharpness: 9    Aberrations: 9    Bokeh: 10    Autofocus: 9    Handling: 10    Value: 9    New or Used: Used    Camera Used: k5   

Bar none, this lens is the best lens in my bag. PentaxForums took a poll to see what the greatest lens was of all time and this lens was second I believe.

At f8
Tack sharp! This thing is amazing with color, contrast, sharpness, I mean you go down the line and it scores 10's on everything. I found the construction to this lens to be on above the top Canikon lenses and have had Canon shooters admire this glass. If you're looking for a do-it-all-focal-length for digital & film, this is your best prime option. I've found the 31 to be my favorite lens in my bag and I can't wait until FF comes out. I would like to take advantage of the native FOV it was intended for.

At f/1.8
At 1.8 this lens is good, but not amazing. sharpness lowers dramatically, but all-in-all, the lens is pro glass.

You're paying for what you get in this case: an amazingly built quality piece of top Pentax engineered glass. PM me with any questions and I'll try to answer asap.
Senior Member

Registered: April, 2015
Location: Boston,MA
Posts: 257

6 users found this helpful
Lens Review Date: November 30, 2016 I can recommend this lens: Yes | Price: $720.00 | Rating: 10 

Pros: IQ,rendering, bokeh
Cons: size, a bit soft at 1.8, price
Sharpness: 9    Aberrations: 9    Bokeh: 10    Autofocus: 9    Handling: 10    Value: 8    New or Used: Used    Camera Used: K1   

First of all, I like the focal length a lot, 28mm is a bit wide and 35mm sometimes is not wide enough for me. 31mm is perfect on the FF for me.

Not razor sharp below f2, but still pretty good, perfect for portrait. Once you step down to 2.8 the sharpness jumps to a different level.

Rendering of this lens is just special,not as contrasty as the ZK 35 but the overall feeling is slightly better than the ZK .Another great thing about this lens is that it's sharp at all distant,so you can use it for landscape, street shooting and portrait, not like my M28mm f2 , which is great at close distant but not so good at infinity.

Last but not least, the bokeh. IMHO the 31mm produces the best bokeh I've seen from a wide angle lens, the transition from in focus area to OOF area is so smooth.

Cons:it's not cheap and I wish it can be a little smaller just like the 43&77, it would be great to add WR in the future.
Overall, this is probably my favorite Pentax lens.


Registered: January, 2009
Location: East Bay Area, CA
Posts: 6,124

6 users found this helpful
Lens Review Date: October 20, 2011 I can recommend this lens: Yes | Price: $950.00 | Rating: 10 

Pros: build quality, bokeh, fast lens, sharp wide open
Cons: short hood, price
Sharpness: 9    Aberrations: 8    Bokeh: 10    Autofocus: 10    Handling: 10    Value: 9    New or Used: Used   

I purchased a nearly new AIV copy and remain amazed at what a wonderful lens this is. I wanted to give a 9.5 but rounded up to a 10 (i have never given a 10 in these reviews, but this is perhaps the one lens i've owned which may actually deserve it!).

Like the other FA limiteds, the build quality is exceptional, solid metal construction and lovely to behold. Manual focus is a pleasure and IQ is excellent. It is hard not to want to shoot everything wide open with this lens however because the f/1.8 sharpness is far better than i would've expected. And then there is that lovely bokeh. I have a few favorite bokeh lenses that are amazing (FA77, Cosina 55, etc) and have to say i'd put this among the others. This is my widest "bokeh lens" and quite easy to grab first for a full length portrait or flower close up shot.want to use this instead of any 30-ish focal length on a zoom lens. Sure, i wish the price were less but for the quality, it is actually quite reasonable. It is not even in the top 5 most expensive lenses i own anymore, so the pain of that purchase has been attenuated since I first posted this review.

negatives (which are far outweighed by the positives):
- some detectable CA on the high contrast areas. same or less than with the FA77, not a biggie and completely correctable in ACR.
- hood is not optimal for crop sensors so i keep a larger hood attached. Adding a filter ring(square filters) is a little fiddly, but I found a good solution and never think twice about it.

that's it, as soon as you can get this lens, do it!! It lives up to the legend.

this is a pano:

Registered: January, 2011
Location: Skåne, Sweden
Posts: 455

5 users found this helpful
Lens Review Date: August 10, 2014 I can recommend this lens: Yes | Price: $950.00 | Rating: 8 

Pros: Build quality, unique offering, character
Cons: Value, focal length on APS-C
Sharpness: 8    Aberrations: 7    Bokeh: 9    Autofocus: 7    Handling: 9    Value: 7    New or Used: Used    Camera Used: K-5, K-3, K-01   

This review is for a mint condition silver 'Made in Japan' FA31 bought second-hand in Sweden, serial nr in the 0027xxx-range.

  • Build quality
  • Look and feel
  • Unique offering (like all other Limiteds)

  • Inconsistent autofocus
  • Wide open sharpness
  • Value for money

  • General purpose (normal lens on APS-C)
  • Low light
  • Travel

The first Limited I got was the DA40, and soon I started to buy them one by one as mint second-hand samples came on the market. After a couple of years I got all the DA Limiteds and I was pretty well covered (I don't shoot much longer telephoto). There was something mythical about the FA Limiteds though, so after a while I started to look for them as well. The FA31 was the last one I got of the "three amigos" (FA31/43/77).

Most of my serious work is portraits and I was well covered with the FA43/77 AND DA40/70 (the plan was to sell the DA's, still haven't a couple of years later...). I get that at fast wide-angle is expensive, and considering the parameters of the FA31 for what it offers on full frame it is simply outstanding.. but on APS-C it becomes a pretty expensive normal lens.

To go trough the basics first. The lens is sharp. Like all lenses it is softer wide open, but it builds up gradually. It is sharp enough to use wide open for most applications, but I still feel a little bit disappointed. If I don't need the speed I will stop down to f/2.2 for a boost in sharpness. With nine apertures blades it the bokeh stays nice at most apertures, so you don't need worry about stopping down with respect to that. The bokeh is very pleasing, with a bit of character as well, just as I like it! One of the drawbacks of the lens is various aberrations, where lateral is an easy fix in PP, but where longitudinal is not. It might be disappointing if you are looking for perfection, but it hasn't bothered me. It adds to the character, just beware of it before spending the cash. I've read a few comments about "medium format feel" on APS-C, and I get that a fast wide angle is rare and shallow DoF with that wide (not so wide on APS-C) angle is not so common, but I don't feel that the FA31 offers something that other similar combinations would in that respect.

Autofocus is fast, but not as fast as the DA Limiteds. I don't mind the screw-drive noise, but in these SDM-days it is worth mentioning. I have used the DA*50-135 for a while and even though it has SDM it was slower than the Limited-lenses (although more silent). Also I wouldn't think that I should miss quick-shift from my DA Limiteds, but I guess that I use it more than I thought. It can be small situations like when you are about to put the camera in the bag, you want to retract the lens (focus to infinity), and then you have to fiddle with the AF/MF-switch on the camera. Small things, but I think it is worth mentioning. Build quality is otherwise on par with the DA Limiteds, which is to say very good - tight tolerances, nice materials. The aperture ring has a very slight play though, but as does my FA43 and FA77, so I think it is supposed to be like that. The leather case of the FA Limiteds are a bit sturdier than the DA Limiteds, also the cap has a nice green felt, great premium feel The size of the lens is pretty small, but I just keep thinking that it would be really amazing on a FF sensor, now it is more what the FA43 would have been on FF. A letdown if the FA31 is autofocus consistency. On the K-5 it both front- and back focused so I rarely used it even near wide open, but on the K-3 it has gotten better (not perfect though). Actually, it fits very well on the K-01 and with its contrast detect it doesn't show the front/back focusing problems. It is also a good match for both size and looks It is not optimized for manual focus though, focus throw is very short (as with most AF-glass), but has a slightly longer throw than the DA-series.

I have mixed feelings for this lens. It is not perfect, with a few aberrations and focusing problems (phase detection). It also goes from being a rare fast wide angle to becoming "just" a fast normal lens on APS-C. I keep thinking how wonderful it would be on FF (and that has been shown on film and the Sony A7-series). But, I don't feel that there is any real replacement. It has a nice character, it serves several purposes, and it has a very nice build and feel. If you are willing to compromise there are options like the Sigma 18-35, FA35/2, DA35/2.4 or Sigma 35/1.4. Each is a compromise of build quality and/or size, although they are cheaper

Pentax K-01, SMC Pentax-FA 31mm F1.8 Limited. 1/80 sec at f/2.0, ISO 1600.

Pentax K-5, SMC Pentax-FA 31mm F1.8 Limited. 1/60 sec at f/3.2, ISO 100.

Pentax K-3, SMC Pentax-FA 31mm F1.8 Limited. 1/180 sec at f/4.0, ISO 100.

My pictures on flickr with this lens
Site Supporter

Registered: December, 2018
Location: Vancouver Canada
Posts: 29

4 users found this helpful
Lens Review Date: February 23, 2019 I can recommend this lens: Yes | Price: N/A | Rating: 7 

Pros: Great for low light
Cons: Terrible CA in harsh light!
Sharpness: 9    Aberrations: 5    Bokeh: 10    Autofocus: 9    Handling: 8    Value: 6    New or Used: Used    Camera Used: K1   

I was very excited to have an opportunity to borrow a AIV 31mm from a colleague at work for several weeks. I own a FA 35 f2, the FA Limited 77, and the DA HD 20-40 Limited (APS-C) as well.

This review is a comparison of the 31, 35, and 20-40 lenses on the K1.

Image quality
The 31mm is very very good in low-to-soft light, and the bokeh is in a completely different class from the FA 35mm than I would have imagined. Exposure metering is better on the 31mm too. Low light, shallow DOF appear to be the strengths of this lens, and it makes for a good portrait lens.

Sharpness of the 31mm and 35mm were equal. I could not detect a difference.

In harsh light, the 31mm showed massive purple fringing in high contrast areas; as bad as the FA 35. Given the reputation of this lens, I am really disappointed.

Another surprise: the DA limited 20-40 [zoomed to 31mm f3.5] on the K1 was nearly as sharp as the FA 31mm at 3.5! The FA 31 has much less vignetting of course; but what surprised me was how usable images with 20-40 are on full-frame.

The 31mm is solid and enjoyable to use; and on a APS-C body nicely balanced. The K1 however is already heavier than I would like, and I prefer the lighter plastic weight of the FA 35. T he 31mm made it impossible for me to shoot the K1 a single-hand.

The 31mm is a great lens, but is it worth the significant cost over the FA 35? For me, it would have to be significantly better than the FA 35 and even the DA 20-40 (which I am now using with the k1). With serious CA in harsh lighting, I hesistate to use this lens outdoors on a bright day. Perhaps a future 31mm with HD coatings will appear, and then the value equation will improve.
New Member

Registered: June, 2017
Posts: 2

4 users found this helpful
Lens Review Date: November 4, 2017 I can recommend this lens: Yes | Price: $750.00 | Rating: 10 

Sharpness: 9    Aberrations: 8    Bokeh: 10    Autofocus: 10    Handling: 10    Value: 10    New or Used: New    Camera Used: KP   

As a long-time Pentax user I got little annoyed by the acclaimed "legendary" status of this lens, and felt no urge to fill the gap between my two most used leses, DA21 and FA43. Both lenses show their quality even better with the brilliant new KP sensor. But curiosity prevailed when I saw a mint silver made-in-Japan FA31 for sale. For a Limited lens it is bigger and heavier than what I was used to. But after the first day of shooting in the streets of Amsterdam, I was "sold" completely. It has exactly the same thing that makes Leica lenses (I used an M9 for some time) so special ! Numerous people have tried to explain what that is. It's price may be an issue, but look at the "mirrorless" world today, where top grade primes are mostly priced well over 1K, and have sizes that dwarf the camera body. This piece of heavy metal balances very nicely on the little KP (also aesthetically)

Registered: October, 2012
Location: Colorado
Posts: 1,422

4 users found this helpful
Lens Review Date: August 20, 2013 I can recommend this lens: Yes | Price: $989.00 | Rating: 10 

Pros: Sharpness, Contrast, Color Trueness, Construction, AF Speed, Fixed Lens Hood, Aesthetics
Cons: Sometimes it's too sharp.
Sharpness: 10    Aberrations: 10    Bokeh: 10    Autofocus: 9    Handling: 10    Value: 10    New or Used: New    Camera Used: K-7, K1000, KM, KX, K2, K-3, K-S1, K-S2   

I've used the 31mm FA Limited for about seven months now and feel I can finally write a reasonable and informed review after my recent trip to Japan with it. In three weeks, I shot about 7,000 photos with this camera at the beach, near the ocean, being splashed by some inconsiderate jerk at the ocean, inside a bulk fuel storage tank, inside an incredibly hot fuel pump house, in two thunderstorms, and in a crowd exceeding 20,000 people. In every situation, the lens performed beautifully on both the Pentax K-7 and Pentax K1000 that I brought on the trip.

Note that during rain, when I was splashed, and in a very-find-dust environment when entering the fuel tank I kept the camera wrapped in plastic to prevent water and dust from getting into the lens. This lens is NOT weather sealed (I don't think it needs to be) and should be protected in harsh environments.

This is the sharpest lens I own. I use it for photographing people, objects, and architecture. In each case, it performs well. The AF is fast enough to focus on people moving quickly at sporting events. But sometimes the lens is TOO sharp. With some people, the lens captures so many details as to make portraits unflattering. In some cases, this lens has made the people I photograph look about ten years older. Typically, the lens is honest in how it portrays people, but for people with wrinkles or lines, it grabs onto them and really makes signs of age apparent.

For architecture and product work, this lens is tops. I think my photos will speak for themselves.

This lens, today, is going for between $1,200 and $1,300. I picked it up for $989 a couple years ago. Could I justify up to $300 more if I needed to replace this lens -- YES. Emphatically yes. This was a great purchase and has, in very short order, become one of my workhorses and a keystone in my lens lineup. In fact, this lens' quality spurred me to pick up the 77mm FA Limited lens last month.

K-3 Samples:

K-S1 Samples:

K-7 Samples:

With my K1000:
Forum Member

Registered: April, 2010
Posts: 91

4 users found this helpful
Lens Review Date: February 17, 2013 I can recommend this lens: Yes | Price: $950.00 | Rating: 10 

Pros: Sharpness, background blur, uniformity across the frame
Cons: somewhat hefty, built-in hood not very useful
Sharpness: 10    Aberrations: 9    Bokeh: 10    Autofocus: 10    Handling: 10    Value: 10    New or Used: New    Camera Used: K-5   

I was longing for this lens for a couple of years. I hesitated to buy it because it was somewhat pricy and I had DA* 16-50 which produces really great images around that focal length, even wide open.

However, I had had FA77 and wanted something in the same league for wider angle shots. Finally it was time to upgrade the aging K-7 I had and I couldn't resist any longer and ordered FA 31 as well.

The first impression was rather disappointing because it just wasn't sharp the way I expected wide open. FA 77 was much better at 1.8 in comparison. However, stopped down to 2.2-2.8 the sharpness of FA 31 was just brilliant in center and across the frame.

Another source of disappointment was the lack of expected 3d effect. I can point FA 77 pretty on everything and it magically produces an appealing image, often having that 3d feeling. I couldn't do that with my copy of FA 31. I blame "Assembled in Vietnam" stamp as opposed to "Made in Japan" of FA 77 but not sure since I don't have another copy to confirm that.

It was not that I didn't like it, I found it amazing at landscapes or group shots at f/4.0-5.6 but taking photos at 1.8 was something I couldn't afford myself. I decided to wait until I get used to it before making final judgement.

Now, after a year passed, I think I've finally found the way to use it properly. The point is that the lens open at f/1.8 produces great, sharp images when distance to subject is very close. I'm not sure if this is a design flaw or some feature of this lens copy or just focusing issues but now I don't hesitate to shot wide open when choose the subject properly:

All in all it is a superb lens and the competition's equivalents are just monstrous, albeit a stop faster. I hesitate to switch brands because of great Pentax FA 31 and FA 77 lens - there is simply no substitute.
Veteran Member

Registered: February, 2007
Location: Vancouver, BC
Posts: 613

4 users found this helpful
Lens Review Date: September 25, 2011 I can recommend this lens: No | Price: $1,351.91 | Rating: 8 

Pros: Does what it was designed to do perfectly.
Cons: Questionable QC. Most aspects of the lens hood.
Sharpness: 6    Aberrations: 8    Bokeh: 8    Autofocus: 8    Handling: 9    Value: 3    New or Used: New   

Bought first copy new.
It was AIV. Shockingly soft wide open until about f4. Sent it back and had to fight for a MIJ version. This was much much much much better. Pretty darned sharp from wide open up. Still had some slight issues for my style.

On the whole, this was a lens bought based on reputation and not need, so I fully expected its performance to wow, but it didn't.

The value for money is downright bad. Focal length is extremely common and there are much saner options available. For this much $$$, the first copy you receive should be bang on, not the second and that after pleading.

All in all it was like speed-dating gone bad, and I decided to sell it to recover some funds.

EDIT 13-05-2012:
I must add, however, that in the right hands with someone who knows how to use it, this lens will produce fantastic images. Unfortunately, I am not in that camp.
Junior Member

Registered: June, 2010
Posts: 47

3 users found this helpful
Lens Review Date: March 4, 2013 I can recommend this lens: Yes | Price: $750.00 | Rating: 10 

Pros: Bokeh, Sharpness
Cons: Price
Sharpness: 10    Aberrations: 9    Bokeh: 10    Autofocus: 9    Handling: 10    Value: 9    New or Used: Used    Camera Used: K-5 iis   

I will make this one short. Do not expect sharpness across the frame at wide apertures. I am cracking up with some of the reviews that list that as a downside. If it was sharp across the frame at 1.9 we could pretty much throw away the ‘bokeh’ category… because it wouldn’t have any. That is one of the main benefits to using a wide aperture. Also folks, aperture has a relation to focal distance. Don’t expect a sharp image if you are shooting a landscape at infinity at f/2.

I would say the strongest point of this lens is the bokeh. One of the smoothest around. Produces excellent ‘portraits.’
The sharpness is the second strong point. The slice of focus at the wider apertures is very sharp.. but granted, it is just a small slice at the wide end, as it should be.
A little bigger than most primes of this focal length but it is a good universal size and weight for most cameras.

That is my short review as many others have said the rest. Love this lens!
Site Supporter

Registered: October, 2008
Location: Vancouver, Canada
Posts: 6,198

2 users found this helpful
Lens Review Date: March 5, 2017 I can recommend this lens: Yes | Price: $1,250.00 | Rating: 9 

Pros: Sharp, fast and great handling.
Cons: A bit overrated, cheaper lenses are just as good optically.
New or Used: New    Camera Used: Pentax film bodies (K1000, KM, KX, K2, K2DMD, ME, MX, LX, Super A/Program, P50)   

The FA31/1.8 was released in 2001 and is still in production today. Pentax produced a similar focal length K30/2.8 from 1975 to 1984, so you could consider the FA31/1.8 a refresh of that older manual focus lens. The FA31/1.8 is also the third and last of the FA Limited’s lenses to be released.

Excellent, which should be no surprise considering the cost of the FA31/1.8 and the optical “extras” added to the lens. (Aspherical element, high-reflection low dispersion element, anomalous dispersion element & a floating lens system)

Focal Length:
I find the 30-31mm focal length on FF is not quite wide enough when I’m choosing a single wide-angle for a three prime lens travelling kit and usually go for something wider, like a 20-28mm lens. I find the 30-31mm focal lengths work better as a second wide in a larger kit along with a 20mm lens or as a one lens option on a day trip.

On an APS-C camera you have the perfect “normal/standard” focal length, so I can see why the FA31/1.8 has been so popular on digital over the last decade.

The build of the FA31/1.8 is good for a FA Series lens, but is not as solidly built as any Takumar/K/M Series lens I own.

The FA31/1.8 is a nicely sized well balanced lens that is easy to handle and the best out of the three FA Limited’s. I have no issues manually focusing the FA31/1.8 or using the aperture ring. The distance scale is the “compressed” style, but you get used to it. Overall not bad for an Auto Focus lens.

The FA31/1.8 has a built-in “tulip style” lens hood and accepts 58mm filters, which screw-on inside the ridged hood. The lens cap is a push/slip-on like the rest of the FA Limited’s and is also prone to falling off. I’ll substitute it with an older Takumar 58mm lens cap when I’m travelling, so the OEM cap doesn’t get lost. The FA31/1.8 originally came with a red soft lens case marked “PENTAX 31/1:1.8”, which was later replaced with a black one.

F1.8 is very fast for a wide-angle lens and it makes the FA31/1.8 the fastest wide angle lens ever made by Pentax. (Excluding the prototype M35/1.4)

The FA31/1.8 vs my favourite 28-30mm wide primes:
I also own the K30/2.8 and several 28mm lenses, my favourite being the K28/2. All three lenses have excellent middle aperture sharpness and I don’t really see any difference between the three. The K28/2 is the best wide open and the FA31/1.8 the worst, though I’m unlikely to ever use any of these three lenses wide open. (Note it’s hard to evaluate/compare these three lenses wide open as each lens has a different maximum aperture & focal length.)

Build/handling wise the two “K” Series lenses are better and the K28/2 has the best minimum focusing distance. The FA31 wins the speed race, but is the least wide of the three.

The K28/2 however has a “3D” effect that I just don’t get with the other two lenses, so that’s by far my favourite wide angle lens overall. There is something about the legendary Pentax/Carl Zeiss designed K28/2 that is magical, the FA31/1.8 & K30/2.8 are excellent but not in the same league.

I rated the K28/2 a perfect 10 and the K30/2.8 a 9.5, the FA31/1.8 also gets a 9.5.

The FA31/1.8 is an excellent wide angle lens, however there are much cheaper manual focus options that are just as good or better overall.

I bought my FA31/1.8 from an online camera store and paid $1199.00 Euros. It was in LN condition, boxed with all the original paper work. It’s a silver low serial number MIJ, with a red soft pouch.

Sample shots taken with the FA31/1.8. Photos are medium resolution scans from original negatives. Both shots were taken in Vancouver.

Camera: P50 Film: Kodak Portra 400 ISO: 400

Camera: Super A Film: Kono Kolorit 125T ISO: 100
***Note this is old expired Kodak Tungsten movie stock film, so yes it's grainy***

Site Supporter

Registered: April, 2015
Location: Wisconsin, USA
Posts: 2,148

2 users found this helpful
Lens Review Date: April 13, 2016 I can recommend this lens: Yes | Price: $475.00 | Rating: 10 

Pros: Great color and bokeh, built like a tank
Cons: Not super sharp wide open
Sharpness: 9    Aberrations: 9    Bokeh: 10    Autofocus: 10    Handling: 10    Value: 10    New or Used: Used    Camera Used: K3ii   

I recently purchased a used 31mm lens. Boy was it beat up, it was really "ugly". I've shot it extensively for about one month now and found that it works like a new lens, and it still makes wonderful images. Auto-focus is dead on although of course not the fastest. This lens is built like a tank, and will just keep on working - period! Now that's quality!

The colors it produces are exceptional as is the bokeh.

Could be better at f/1.8 and f/2, but hey, no lens is perfect - though this one is very close.

I spent a day comparing this lens to my Zeiss ZK 35mm f/2 lens. Overall, I just liked the IQ of this Pentax 31mm lens a bit better, so I've put my Zeiss 35mm lens up for sale.

I also compared this lens to my Sigma Art 18 - 35mm f/1.8 lens. At 31mm, the Sigma is a bit sharper at all apertures than is the Pentax 31mm lens. Also, at f/1.8 and f/2, the Sigma Art images are overall better than the Pentax 31mm. However, the Pentax 31mm lens has this terrific rendering that's just hard to describe. So, I'm keeping both lenses. Will use the Sigma where precision is needed, and will use the Pentax where I am going for an "artistic" rendering.
Add Review of SMC Pentax-FA 31mm F1.8 AL Limited Buy the SMC Pentax-FA 31mm F1.8 AL Limited

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