Lens Spotlight: K135 - Jason Doss

Lens Spotlight

smc Pentax-K 135mm f/2.5

This 135mm lens was among the fastest of its day, and one of the standout examples of excellent optical engineering available in the mid-1970s. This is the middle of three 135mm lenses in my collection, definitely smaller and lighter than the previously discussed A*135, but likewise heavier and larger than the yet-to-be described M135f3.5.  This focal length is typically used for portraits at a distance, tight fact or head/shoulders portraits, enhanced bokeh, or photography where subject isolation is required. Here is an informative article on why one might want to have a 135mm lens in their collection.


The lens is 500g (1.1#) and, focused at infinity, 86mm long (3.4 inches) and has 8 aperture blades and 58mm filter threads. The fast aperture of f/2.5 was among the fastest available at the time, but has since been superseded by lenses with max apertures below f/2. The lens bears the usual aperture ring and has a rubberized grip for easy manual focusing. Minimum focus distance is 150cm (4.9 ft) producing 1:9 reproduction ratio (0.11x).

The K135 was an early purchase, selected due to an affinity toward telephoto lenses, and because it was the fastest lens available at the time that didn't represent a significant financial investment. Being unsure of the staying power of mirrorless and manual focus lenses at the time, I wanted to have a modest but sensible collection. Obviously, that philosophy has gone clear out the window, but nevertheless the K135 was a great investment in a lens that performs well on digital and film.  Handling is excellent, weight balance is great on the K-1 mII (but it was front heavy on formats it was not designed for), and focusing is smooth and accurate.


The only significant flaw, and this is a flaw common among many telephoto lenses of this period, is chromatic aberration. This shows up as colored fringes at areas of high contrast. An example might be a window frame, shot from the inside on a bright sunny day. The edge of the frame might show purplish or greenish borders, and this is due to the design of the lens which wasn't made for digital. Film doesn't react like this, or if it does, it's much less significant.  Digital does because each pixel on your sensor reacts to only one color, then math (ack!) is done to combine the pixels into a smooth image. The only solutions that I can think of for this problem are three:  First, avoid or minimize such situations.  Look for an angle where your subject is not back lit. Second, convert your image to black and white.  No color, no color fringes! Third, use RAW and process with superior software.  I use Lightroom, which may not be "superior," but does offer a one-step correction tool that does a pretty good job removing this problem in most images.


And now the moment you've been waiting for, a brief description of the images I've decided to show from a recent outing with this lens.  Topside and bottomside are shots of the departure of Union Pacific 4014 which is (I believe) the last functioning steam engine.  The train left Kansas City Union station at about 8am, and much of what we could see from our very good perspective on a bridge over the tracks was in deep shade, and the sun was rising behind it. This made for some harsh backlighting in areas that I ended up cropping out.  The top photo is a 1920's model Kodak hand-crank video camera, unmanned at this time. The owner/operator was never seen. Bottom is the Big Boy himself, approaching ground zero. The center shot is the last sunset I'll ever shoot from apartment 2701 in the KCPL building in downtown KC. This is a pixel shift shot, an image processed from precise alignment of four frames for true color and high resolution.


Please be aware that all photos to the left are cropped thumbnail-like images due to the website building software I'm using.  Click any photo to see larger versions with the full field of view.  Comments can be left on this page or under each photo if you are so inclined.


That's all I have for now... See you next time.


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