Pentax SMC-K 135mm f/2.5 - Review / Lab Test Report
Lens Reviews - Pentax
Tuesday, 25 December 2007 18:34
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Special thanks to Ruediger Neumann for providing this lens!


Ruediger has supplied lots of new Pentax lenses for testing and he also sneaked a specialty into the last package - an old Pentax SMC-K 135mm f/2.5. The lens is about as old as time itself ... well, make it the late 70s/early 80s - the pre-AF era. In fact the K 135mm f/2.5 doesn't even offer aperture priority on the K10D (due to the crippled KFA2 mount here) and you have to use stop-down metering using the camera's green button. The selected aperture is not visible in the viewfinder. So you may ask why bother anyway ? Well, SMC-K/M/A lenses are usually dirt cheap on the used market and some may come in handy regarding the current deep dark gaps in the Pentax lens lineup. Besides it is surely interesting to have a look how a (sort of) stone-age lens behaves on a current APS-C DSLR. In this scope the field-of-view of the K 135mm f/2.5 is equivalent to about ~205mm on classic full format cameras.

In terms of build quality the SMC-K 135mm f/2.5 feels like a rock. Even after 30 years it makes many current AF lenses look like cheap toys. The broad, rubberized focus ring operates exceptionally smooth and very well damped. The lens extends a bit when focusing towards close distances.

Equiv. focal length202.5 mm (full format equivalent)
Equiv. aperturef/3.8 (full format equivalent, in terms of depth-of-field)
Optical construction6 elements in 6 groups
Number of aperture blades8
min. focus distance1.5 m (max. magnification ratio ?)
Dimensions68 x 86 mm
Weight500 g
Filter size58 mm (non-rotating)
Hoodbarrel shaped, snap-on type (optional)
Other features-