Pentax SMC FA 31mm f/1.8 AL: A Powerful Old School Lens

Pentax SMC FA 31mm f/1.8 AL Image

Pentax SMC FA 31mm f/1.8 AL DEALS

The Pentax SMC FA 31mm f/1.8 AL is an old school looking lens, verging on wide focal length in Pentax‘s Limited series. Favored as a good performer, the FA-31 is getting quite old now, but can it still produce the goods?


Back in 2001 when film cameras were still big, this type of lens didn’t stand out for its looks. These days, with lenses looking sparse on the barrel, it does look decidedly old school. This isn’t a problem, however, if the lens performs well.

The FA-31 is almost in between focal lengths as most would go for either go for a 28mm or 35mm instead of the 31mm which gives a slightly different perspective. It works well as a general wide-angle lens.

The first observation with the lens is that it comes in a sleek silver color, adding to its old school looks. Standard black is also available, but if you have the option, silver is the color to go for.

The Pentax SMC FA 31mm f/1.8 AL includes a K-mount with optional adapters available to mount this lens on other camera brands. The focal length ranges from f/1.8-f/22 with nine aperture blades, and a 70° angle of view. The filter size is 58mm and the whole lens weighs in at a reasonable 345g.

The outer barrel is made of aluminum, built extremely well, and looks and feels both vintage and new at the same time. It’s not weather sealed, but on it seems to take at mild rain and dust in stride.

Pentax SMC FA 31mm f/1.8 AL Image

The focus ring has a cool double ridge to it but turns in the same direction as Nikon lenses, so no problem if this is what you’re used to. There are the usual distance scale and lens aperture ring with stop markings. One nice benefit of this is that the aperture ring has a nice click when moving positions, similar to how a fully manual lens feels. There’s also a permanent petal-type hood.

In Use

When focusing, you have to go manual with this lens. It takes a little bit of getting used to, especially the direction of the focus ring, but you soon get into a routine that works for nail sharp images. The 90° of rotation makes sure you hit the sweet spot quickly and produces surprisingly more keeper shots than expected. From 0.3 meters to infinity, it actually starts to become quite fun once you start nailing the focus. Basically, no complaints with the operation.

On initial impressions, images come out very sharp, even when wide open, but the corners can be a little soft. At f/2.8 the lens sharpens up very well with good overall contrast. Start stopping down and everything gets progressively better with the best being found at f/8. Start cranking the lens beyond this point and diffraction starts setting in. If you want to use this lens for landscapes, it would be f/4 and higher. In general, the Pentax SMC FA 31mm f/1.8 AL is quite capable of giving very sharp images with a high-resolution DSLR.

The lens has reasonable coatings, but as it’s getting on in age, it’s not as good as more modern lenses when it comes to ghosting and flaring. With strong backlighting, ghosting is evident when wide open and really only becomes manageable when stopped down to f/8.

Pentax SMC FA 31mm f/1.8 AL Image

When things like sunlight are directly in view you have to be more mindful, as there are more ghosting artifacts than nice star shapes. Therefore, you have to be mindful of where you place the sun in an image. Speaking of star-shaped, you really have to stop down to get reasonable sun stars and they only become best at f/22. Vignetting is also typical of this type of wide-angle lens, giving 1.5 stops when wide open, but reduces considerably down to f/5.6.

As an f/1.8 lens, the background blur or bokeh is an important feature. Fully wide-open the bokeh is pretty good. Not the world’s best, but smooth and appealing. The colors transition well, and while there is some fringing, it can be easily removed in postprocessing. One thing that’s appealing about the 31mm is a sense of depth with portraits, pulling the subject away from the background very nicely. There’s also an almost old school look to the colors, rich, but when fully wide-open almost a little hazy.

How Does the Pentax SMC FA 31mm f/1.8 AL Compare?

They may not be direct comparisons at a focal length of 31mm, both there are a few comparable lenses at 28mm and 35mm, especially if you want to plant one on a Sony camera. The Sony Zeiss ZM 35mm f1.4 is more expensive, but pound for pound the Pentax is a better option. The Sony FE 28 f2 costs less and is smaller, but all round again the Pentax wins it over.

  Pentax SMC FA 31mm f/1.8 AL Zeiss ZM 35mm f/1.4
Focal Length 31mm 25mm
Elements 9 elements / 7 groups 10 elements / 7 groups
Filter Size 58mm 49mm
Weight 345g 381g


The main question is if the Pentax can hold its own against modern prime lenses. It definitely has a unique viewpoint with a 31mm focal length and there are only a few downsides. The ghosting and flaring aspect isn’t great which may be a deciding factor for some, but in all other areas image quality is very good with a unique look on the world.

Most importantly, the lens gives a very nice depth or even 3D look to images. If you don’t have a lens around this focal length and want a different perspective on the world, then the Pentax SMC FA 31mm f/1.8 AL is definitely worth checking out.

The Review

Pentax SMC FA 31mm f/1.8 AL

The Pentax SMC FA 31mm f/1.8 AL is an old school looking lens with modern performance. Fast and sharp, this unique focal length can still act as a great all-rounder.


  • Price
  • Rich colors
  • Nice bokeh


  • Ghosting
  • Permanent hood
  • Not completely weather sealed

Pentax SMC FA 31mm f/1.8 AL DEALS

Review Breakdown






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