Pentax SMC-FA 31mm f/1.8 AL Limited: A Wide Classic Redefined

Pentax SMC-FA 31mm f/1.8 AL Limited

Pentax SMC-FA 31mm f/1.8 AL Limited

K Madhavan Pillai discovers why the film era Pentax SMC-FA 31mm f/1.8 AL Limited finds its niche in today’s digital environment, especially with the Pentax K-1 full frame.

Primarily designed for Pentax film cameras, the FA Limited series holds a certain automatic fascination for older aficionados, especially after the launch of the highly rated full frame K-1. The 31mm is the widest of the three Pentax FA Limited primes and is known to have delivered excellent performance on film. DSLR sensors differ in a fundamental way when it comes to optical requirements from lenses. They require light paths that are as perpendicular to the sensors as possible, to achieve the best results. This review intend to answer two basic questions… What sets the 31mm apart? And how does it fare with the K-1?

The optics are made of nine elements in seven groups, including a moulded glass aspherical element. Unlike newer lenses, the 31mm has an aperture ring, making the lens suitable for all Pentax bayonet mount film cameras as well as DSLRs. For DSLRs, as with the K-1, the aperture ring should be set to ‘A’ for aperture control through the camera body.

Being from the FA series, the lens uses an older screw-type motor for AF. There is no full time MF override, but the manual focus ring is smooth, well damped and feels quite wonderful in use. The focusing scale is visible through a cut out in the metal, and is accompanied with a wonderfully detailed DOF scale as well. There is an infrared focusing mark. The petal shaped metal lens hood is built in, but its design makes it possible to fit 58mm filters if needed.

A lot of the handling pleasure of the 31mm comes from its design finesse. It is hand-assembled, all metal, and solidly built, compact but nicely weighty at 345 grams. It feels perfectly good on the K-1. Every component of the lens has a beautiful, meticulous level of finish. The markings are engraved, rather than painted on. The DOF scale, in particular, is wonderful to use. Being a scale meant for film and not for the high resolution sensor of the K-1, I constrained DOF slightly, for sharpness at 100%. The advantage of the scale is that it makes it easy to calculate this as well.

There are other small appreciable touches. The lens cap, for instance, is metal, quite deep, and secures firmly because of a green velvet lining. No pinching and fumbling about. Don’t lose this lens cap though! Replacing it would be very expensive, or impossible to get.

Details render well. The level of contrast with colour is also excellent. Exposure: 1/30sec at f/5.6 (ISO 4000)/Photograph/K Madhavan Pillai

Details render well. The level of contrast with colour is also excellent. Exposure: 1/30sec at f/5.6 (ISO 4000)/Photograph/K Madhavan Pillai

The AF response on the K-1 is predictably slower than any of Pentax’s new range of lenses, and not silent, because of the type of motor the lens employs. It works well both in single and continuous AF without hunting (something older lenses are very prone to), but is not able to effectively keep up with erratic action. In any case, the 31mm is not meant for that sort of shooting.

At f/1.8, the 31mm is a sharp lens that will satisfy any photographer, even if it is not as critically sharp as some of the newer primes I have seen in this focal range, especially at similar price points. It also delivers excellent control over definition from center to edges. Where the 31mm exceeded my expectations was with the bokeh, smooth and sensuous.

The older optical design shows its characteristic issues on a high resolution full frame DSLR, especially wide open, with vignetting close to 3 stops. At f/2 and f/2.8, sharpness increases dramatically and vignetting all but disappears. Optical performance peaks at f/5.6. Chromatic aberrations are surprisingly low. There is a slight but visible barrel distortion which can be easily corrected in post.

Many Pentax lenses are known for their unique visual signature. The 31mm is no different. The colour contrast is excellent throughout, but the vignette adds a certain ambience. Combined with the exceptional bokeh, the results are extremely pleasing.

At Rs 74,050, the 31mm Limited is not for a casual user, or for someone who simply wants the sharpest AF lens. If this is what you are looking for, you would be better served by the Sigma 35mm f/1.4 Art, available with a Pentax mount. A more experienced user will appreciate the finesse, superb handling, optics, unique visual signature, and the expanded functionality for MF and IR of the 31mm Limited, and the fact that there are not all that many options for the K-1. Even in comparison with Leica or Voigtländer lenses, the Pentax SMC-FA 31mm f/1.8 AL Limited holds its own, and offers good value for money.

Max aperture of f/1.8, design. DOF scales
Unique visual signature, consistency in sharpness across the frame
Build Quality
Full Metal construction, handmade
Excellent handling. balances well with the K-1
Warranty & Support
Three year warranty, wide service network
MRP Rs. 74,050
Who should buy it? Purists who prefer to work wih Manual Focus, for whom the process is extremely important.
Why? Optical quality, sharpness and bokeh are excellent. The handling capabilities of the 31mm is highly refined.
Tags: Review, K Madhavan Pillai, Lens, better photography, Pentax, March 2017, Pentax SMC-FA 31mm f/1.8 AL Limited