Pentax-A SMC 28mm f/2.8 F2.8

Adam Maas adam at
Tue Jul 13 18:30:14 EDT 2010

On Tue, Jul 13, 2010 at 5:09 PM, Eric Weir <eeweir at> wrote:
> On Jul 13, 2010, at 3:41 PM, J.C. O'Connell wrote:
>> you may want to consider the K28/3.5 version, its
>> reputation is better than both m or a versions.
> It was the fact that aperture can be controlled on the camera body in the A series that attracted me. Perhaps I should be more concerned about quality of images produce, but at this point I only have others' experience to draw on regarding that.
> I'm a bit unclear about K as a lens series versus K as a type of lens mount. Until this thread I assumed all -- or almost all -- Pentax lenses were K lenses. I gather now they are distinct classifications. However, as a reference to a lens series, I think I have yet to encounter a K lens.
> ------------------------------------------------------------------------------------------
> Eric Weir

A brief history of Pentax K mount.

K -Original version of the lens mount. Mechanical aperture coupling
and full-aperture metering. Supports Aperture priority and Manual
exposure modes.

KA - Adds electronic communication of aperture info, A position on
aperture ring, support for Multi-segment metering, body control of
aperture and Program and Shutter priority exposure

KAF - Adds AF and basic communication of lens data (focal length,
current aperture on variable-aperture zooms)

KAF2 - Adds support for powerzoom, extended lens data communication
(MTF data for program lines)

KA2 - KAF2 without Powerzoom or AF support, unique to MZ-M/ZX-M camera

'crippled' KAF2 - KAF2 with mechanical meter coupling removed, no
Powerzoom support, limited or no function with non-A lenses. Early
Pentax DSLR's are this with limited function with non-A lenses (some
film bodies have no function with non-A lenses)

KAF3 - crippled KAF2 with SDM focusing support and basic powerzoom
support. All Pentax DSLR's from the K10D and K100D Super use this

Pentax lens lines:

SMC Pentax - Original K mount lenses, often referred to as K lenses.
Many lenses are holdover designs from the SMC Takumar screwmount

SMC Pentax-M - Compact lenses introduced with the M-series SLR bodies,
replaced most of the common K lenses.

SMC Pentax-A - KA mount lenses, replaced the M series lenses.
Generally improvements optically but build quality declined

SMC Pentax-F - KAF mount lenses, original AF line.

SMC Pentax-FA - KAF2 mount lenses

SMC Pentax-FA L - FA lenses with no aperture ring. Only 3 made and two
were crap consumer lenses.

SMC Pentax-D FA - New digital-oriented lenses which are fully film
compatible. May or may not have an aperture ring, have Quick-Shift

SMC Pentax-DA Digital lenses designed for DSLR-use only, will normally
vignette on film (with a couple exceptions). Have Quick-Shift Focus
(except 18-250)

SMC-Pentax-DA L - lighter, cheaper DA kit lenses. Plastic mounts and
no Quick-Shift Focus.

* - indicates pro-quality lenses. All DA* lenses are weather-sealed
but FA*, A* and M* lenses aren't.
Limited - compact high-performance primes with high build quality
WR - Weather-sealed non-* lenses, all are DA or D-FA.


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