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Pentax-D FA 21mm f/2.4 Review: A Great Lens with Poor Camera Support


Pentax-D FA 21mm f/2.4 Review

If you have been searching for an ultra-wide lens for the Pentax system recently, you likely will come across the $1,400 Pentax-D FA 21mm f/2.4 lens announced late last year. Whether or not you should buy it depends on how much you like Pentax.

The new 21mm f/2.4 lens gives Pentax users a fitting partner for the lineup of FA limited lenses (the 31mm f/1.8 and 43mm f/1.9) and can work well across a wide number of use cases including candid photos of family and friends, architectural work, landscape, astrophotography, or even as a general walkabout lens for street photography.

While there are other “faster” lenses at similar focal lengths, few are as small, lightweight, and sturdy nor do they offer as retro-stylish of a design to show off. While the lens is not cheap, for hardcore Pentax enthusiasts, it is unique enough to warrant at least a test drive. Those who end up buying it, however, are probably going to be only the most discerning of Pentaxians since the lens doesn’t test particularly well, despite what appears to be outstanding performance. The company’s latest full-frame camera is getting long in the tooth and doesn’t seem able to keep up with the new optic.

Build Quality and Design

The Pentax 21mm f/2.4 lens is a very sleek-looking optic with a durable, solid, and weather-sealed aluminum body. While the lens lacks an aperture control ring, there is a large manual focus ring with a big display for the focus range/distance scale. It only weighs 416 grams and is just 3.5-inches long (2.9-inches in diameter), and it is a bit heavier on the backside of the lens making it pretty well balanced when mounted onto a body like the K-1 Mark II. The lens itself is available in two versions: either black (which I tested) or a silver “vintage” design for those looking for something with even stronger retro vibes.

Pentax 21mm Front View

The lens elements consist of four extra-low dispersion (ED) elements and one Super ED glass element which the company says work together to provide the absolute minimum chromatic aberration and fringing possible. There is a built-in lens hood on the lens that is permanently attached to the lens body, and at first glance, it appears there is no way to attach a filter system like a circular polarizer (CPL) or neutral density (ND). The good news is the limited FA lens actually has a small 67mm filter thread just inside of the hood that makes for easy mounting and adjustments from the left and right side of the barrel.

Something else I particularly enjoyed was the focus ring which was smooth had very very little focus breathing. It has physical limits to its maximum and minimum focus distance which I feel make transitions quick and precise; the limited range of the focus ring makes it possible to make quick adjustments from either extreme with just a single finger.

Performance and Usability

Shooting manually, the lens is a breeze to use since the focus is incredibly easy and fast to pull from one extreme to the other. I was able to precisely dial in the area of focus I was after. While the lens and images were great when shooting manually, the autofocus seemed to struggle a bit when the intent was to capture people or objects in a wider scene.

I tested this lens out during a game of hockey and some crowded street scenes and the autofocus (on the K-1 Mark II body) tended to try and grab on to the “wider scene” rather than the people moving through it. I don’t appear alone here, and a brief search indicates other users have had this issue as well and a firmware update for this particular camera may address the issue. This problem is not a “lens” problem, apparently, but worth noting for anyone interested in this lens who is planning to use it with a K-1 Mark II body.

Wide angle hockey player shot with missed focus

While the autofocus was not as snappy on this lens as I would have liked, it was quite easy to manually dial in the focus using the focus ring. And while I wasn’t always a fan of its performance, the AF motor on this lens was incredibly quiet, making it quite useable for shooting video.

I noticed while doing some general testing that when shooting outdoors in daylight and “center balanced” on the exposure meter, photos tended to actually be a little overexposed, and I needed to dial down the highlights or exposure by just a little to truly have a balanced image. I actually found that dialing the exposure compensation dial down to a -.03 on camera seemed to level things out a little better there.

This is again probably an issue with the camera and not the lens, but considering Pentax doesn’t have a newer full-frame camera and this is a full-frame lens, these issues are unfortunate and unavoidable.

As for general use, using the lens on various subjects from wide landscapes to close-ups and even images of my dog, it felt as though it is best suited for close-up subjects because of the incredible fall off when using it wide open. The vignetting was a tad extreme at f/2.4 but the bokeh and separation from foreground and background were just absolutely gorgeous, even in what many would consider to be boring settings.

pentax 21mm f/2.4 Close Up Dog Portrait - Bokeh Test 1

pentax 21mm f/2.4 Close Up Dog Portrait - Bokeh Test 1

Image Quality

Pentax says the FA 21mm f/2.4 lens is the first of its kind that has been optimized for digital photography with an advanced optical design that provides edge-to-edge sharpness. Honestly, for a 21mm lens, I was surprised at how little distortion there was around the extreme edges. Granted, there was some extreme vignetting in the corners when shooting wide open at f/2.4 that slowly tapers off until about f/5.6. But realistically, that is only a potential problem and is pretty easily fixed in post with most editing software and some tweaking to the lens profile settings.

As mentioned above, the bokeh and separation when shooting shallow are very nice with a very fast and visually pleasing falloff between the subject and the background. Regardless of the aperture, the subjects in the frame are consistently sharp with very little distortion (barely noticeable unless looking for it specifically). In fact, no lens profiles have been applied and no distortion adjustments have been made to any of the images included in this review.


Shooting at f/8 and higher you tend to lose some of the “character” the 21mm FA lens offers, but when used in the right settings like the urban, street, and landscape, the results speak for themselves. Users are left with clean and sharp images with incredibly vibrant colors and minimal flaring or fringing.

Freeway long exposure with pentax 21mm lens

Pentax 21mm f/2.4 Sunset Landscape

Below are some more sample images taken with the lens.

A Fabulous Lens with Poor Camera Support

The Pentax-D FA 21mm f/2.4 lens is designed to offer a distinct signature at both distant and close subjects and it does offer that. While it may not test well, it did leave me with incredibly pleasing images and it fits in quite nicely with the rest of the Limited FA lens line up providing users of this series of lenses with a very versatile set of primes.

Over the course of my testing with this system, it became clear why and how Pentax shooters would fall in love with it and the rest of the FA lineup. The new 21mm lens is part of the revered limited series of lenses for the Pentax system that has been called “Jewels” by their users, and for good reason. It provides users with a slightly wider than normal focal length that is wide, but not too wide, leaving it suitable for a variety of situations as well as an everyday general use lens and has a distinct visual flair when shooting wide open that is very fun and pleasing to the eye.

I think what puts this lens in a weird in-between, enthusiast place is that Pentax doesn’t have a particularly great full-frame DSLR, at least not in my opinion. The things that held this lens back can be blamed squarely on the aging K-1 Mark II. I would have much preferred to test this lens on Pentax’s very good K-3 Mark III, but that’s not a full-frame camera and thus wouldn’t give this lens its best showing.

It’s a confusing situation that means even among Pentax shooters — of which there aren’t that many when compared to the likes of Nikon, Canon, and Sony — this lens is made for and will appeal to just a small portion. That’s a niche within a niche, and puts the 21mm f/1.4 in a sort of “collector’s” space to me until Pentax can rectify the camera side of this equation.

pentax 21mm f/2.4 Top view

Are There Alternatives?

Luckily there are several lenses available for those seeking something a little less expensive in a similar focal range, including the Pentax 21mm f/3.2 AL for $496, the Pentax DA 35mm f/2.4 AL lens for $146, or the closer priced Pentax D FA 15-30mm f/2.8 ED SDM WR lens for $1,347 which is bigger and heavier but offers a wider focal range for you to choose from should you not want to be limited by a prime lens.

Additionally, users can look into third-party lenses for the Pentax with lenses like the Sigma 30mm f/1.4 DC HSM Art for $499.

Should You Buy It?

Maybe. For Pentax full-frame shooters who already have the other lenses in the FA Limited line-up, adding the $1,400 Pentax-D FA 21mm f/2.4 would be welcome, as it is a great lens that they will surely love. But, objectively, it doesn’t perform at a level that matches its asking price because Pentax’s older K-1 Mark II seems ill-equipped to handle its excellent optics.


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