Pentax-K 28mm F3.5 under review

I didn't exactly need another 28mm lens. If you doubt that statement you can read my previous comparison of this focal length, or jog over to the Great Vivitar 28mm Bestiary. Yep, I own dozens. Nonetheless, here I am with my latest purchase, the "smc PENTAX 1:3.5/28" (to give the formal name). In this article I will provide an overview of the lens and present some photographs. 

As you may know by now, the so-called "K" series of Pentax lenses was the debut line produced for their SLRs. These cameras used the bayonet K-mount, replacing the universal M42 screw mount used by earlier Spotmatics and Takumar lenses. This line is known for sold metal builds, longevity, and excellent handling (including half-click aperture stops). They work very well on today's mirrorless digital cameras.

Pentax introduced two 28mm lenses in 1976. The famous "SMC PENTAX 1:2/28" was co-designed with Zeiss, who released their own version under the Distagon moniker. The "Hollywood" is a large and heavy beast (69mm long and 425g) with excellent close-focus (30cm) and a 9 element in 8 group optical design. This legendary lens sells for around €1000 if you are lucky enough to find one. 

By contrast the "smc PENTAX 1:3.5/28" is a more reasonable size (47mm long and 260g), though still larger than alternatives in this focal length. It has the same 30cm close focus but is not corrected for that distance. The design is 8 elements in 7 groups which is more glass than most 28mm optics. The most apparent difference is that it is a stop and a half slower. It's not the most plentiful lens, but still easy enough to find.

The Pentax-K 28mm F3.5 has a stellar reputation. You can read many reviews at Pentax Forums, the blog by Phillip Reeve, and other sources. In David Hancock's video it ranks higher than alternatives from Canon, Konica, Minolta, Nikon, and Olympus. Those who know Pentax cannot be surprised by this conclusion. 

My experience concurs exactly with previous findings. This lens has no CA or other visible aberrations. The image is crisp with great colours and high contrast. 

In absolute terms the sharpness of a vintage lens can be exceeded by today's computer-aided designs. But you don't buy a vintage lens for images that will cut your eyeballs. You buy them for unsurpassed handling, (more than) sufficient acuity, and character. At f/8 this lens is as sharp as needed; we are not compromising by any practical measure.

The Pentax-K 28mm F3.5 demonstrates field curvature, in that the corners of the frame are focused in front of the center. This is only a problem if you are photographing a perfectly flat surface without stopping down. Don't do that! Instead, use this characteristic creatively to help isolate a central subject. 

The bokeh is smooth and lovely. Though the faster F2 lens has a natural advantage in rendering a shallower depth-of-field, this model acquits itself well. 

The lens has high vignetting at f/3.5. This is easily corrected in software. Or use it to your advantage (as above). Vignetting is effectively gone by f/8.

Distortion is absent. I happened to take a photo of a tiled grid and was amazed at the results! After correcting for perspective I don't see any notable deviations from straight lines. This might be the most corrected wide angle I own. 

Though I have yet to do a formal comparison with the remainder of my stable, in daily use this lens blows my mind. Is this the best wide angle lens from the vintage era? What I can say is that it's perfect for landscapes shot at f/8 or f/11.

If you have a thousand clams and need incredible subject isolation in a wide angle then consider the Hollywood. If you have about €150 but don't wish to compromise on quality, get this instead. 

Photos were shot on a Panasonic Lumix S5 with my usual processing in Affinity Photo. These are not straight-out-of-camera. 

The images here are too small to properly demonstrate this lens. Instead, check out my images on Flickr. 

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