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Two versions were introduced, one in 1975 and a second in 1977 which differ only in the name plate.  Mine is the older version with "SMC PENTAX 1:2.5/135" on the nameplate.  The newer version appears to differ only in the name, which adds "MM" at the end. The lens has 6 elements in 6 groups and 8 aperture blades.  Minimum focus distance is 150cm (59 inches) with a maximum magnification of 0.11x which can of course be enhanced with diopters or extension tubes.  Speaking of diopters, the front filter threads are 58mm.  The lens is 86mm long (3.4 inches) and weighs 500g (1.1 pounds).

The lens is somewhat heavy but handles very well on the K-1 full frame DSLR.  On lighter or smaller cameras, it may be slightly front heavy, but on my all metal film units it handles well.  Focus action is well damped as the lens extends when focusing close.  The aperture ring goes from f/2.5 to f/32 with half-stop indents between all but the last two apertures, each click stop is audible and clear.  There is a focus distance window at the top that crops out of range measurements, showing only those distances that should be in focus at available apertures.

Wide open performance

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The lens is sharp wide open and fairly easy to focus with the stock K-1 focus screen.  Image quality improves as you stop down, where sharpness increases and aberrations decrease.  Aberrations are easily noted at wide apertures or high contrast areas, however Lightroom's latest "defringe" function works excellently at removing this defect.  Just use the eyedropper on the worst parts of the image and watch it disappear!  

What to use this lens for?  Anywhere a medium telephoto lens has an application.  It's a great travel lens and a decent single-lens solution to shooting candid street photos or architecture.  I use the lens for all purposes, including portraits, outdoor photography including macros and landscapes, pet portraits, and miscellaneous things like architecture and still life photography.

Rating the lens on a scale of 1-10 for Sharpness, Aberrations, Bokeh, Handling, and Value.

The lens deserves a 9 for sharpness.  I'll give it a 6 for aberrations and only because they are easily correctable in Lightroom.  Please remember that this lens was introduced 30 years before digital SLRs, and the problem does not show itself as readily on film.  Smooth transitions and pleasing out of focus areas garner the lens a 10 for bokeh.  I personally like the beefy feel of the lens and enjoy using it, so it gets a 10 for handling.  The lens is an exceptional value also, usually setting you back  $200 plus or minus $50, so I'd call that a 10 for value.  Overall, that averages exactly 9.0.  The lens is almost as old as I am and still very competent on a DSLR, and of course it is fun to use on film too.

Thanks for reading, and please leave a comment below!

Images on Film, APSC, and Full Frame Digital

A Very Good Loaf
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