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Pentax Lens Review Database » Film Era Pentax K-Mount Lenses » K Zoom Lenses
SMC Pentax 28-50mm F3.5-4.5 Review RSS Feed

SMC Pentax 28-50mm F3.5-4.5

Reviews Views Date of last review
1 33,396 Mon April 30, 2012
Recommended By Average Price Average User Rating
100% of reviewers $80.00 7.00
SMC Pentax 28-50mm F3.5-4.5

SMC Pentax 28-50mm F3.5-4.5
SMC Pentax 28-50mm F3.5-4.5

This is the only non-mirror lens of the K series to have varying aperture.

SMC Pentax 28-50mm F3.5-4.5
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (no A setting)
Automatic, 6 blades
10 elements, 10 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
55 cm
Max. Magnification
Filter Size
52 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 55-32 ° / 46-27 °
Full frame: 75-47 ° / 65-40 °
PH-R52 clip-on
Dedicated hard case
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Diam x Length
65 x 52 mm
315 g
Production Years
1975 to 1977
Engraved Name
SMC PENTAX ZOOM 1:3.5 28mm~1:4.5 50mm
User reviews
Manual FocusAperture RingFull-Frame SupportDiscontinued

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Registered: October, 2008
Location: Vancouver, Canada
Posts: 7,967
Review Date: April 30, 2012 Recommended | Price: $80.00 | Rating: 7 

Pros: Small size and focal range on film.
Cons: Variable aperture and two touch design make it cumbersome to use. Too slow at the 50mm end.
Camera Used: K Series film bodies (K1000, KM, KX, K2, K2DMD)   

The K28-50/3.5-4.5 was released in late 1976 or early 1977 and is the first Pentax wide angle zoom. It’s also the first Pentax zoom with a variable aperture and two touch zoom design. The K28-50 was retagged as an M28-50/3.5-4.5 zoom in April 1978. The M version is almost identical, except the K version weights 5 grams more and has a slightly shorter minimum focusing distance of .55 meters. (The M version is .6 meters)

The s/n range was also different between the K and M versions. The K version had a s/n of 5xxxxxx and the M a s/n of 6xxxxxx or 7xxxxxx. This is the same as with the K80-200/4.5 zoom when it was retagged as an M.

The K28-50 has average optics and suffers from some distortion like all these old MF zooms.

Focal length:
28mm - 50mm covers the wide to standard focal range on film and makes a good walk around lens.

The K28-50 is very similar in size and weight to the M24-35 zoom, with the same good build. It’s a good lens for traveling. The K28-50 has a dedicated screw-on metal lens hood with a 52mm filter thread, that's also for the M28-50. The K28-50 is a two touch design which makes the lens cumbersome to use, as you have three rings in a short space. (Aperture, zoom and focus) It would have been better as a one touch zoom and there would be less chance of turning the wrong ring when you are looking through the cameras viewfinder. The K28-50 does not have a DOF scale which is missed on a wide angle lens.

F3.5 is pretty good speed for the wide range, but f4.5 is too slow for the standard 50mm focal length. A constant aperture of f3.5 would have been preferred.

I prefer the M24-35 or M24-50 zooms over the K28-50, so I probably will not be using it very much. The K28-50 will be relegated to my lens “collection” section, as it’s more of historical lens than a practical wide angle zoom.

Sample shots taken with the K28-50/3.5-4.5. Photos are low resolution scans from original slides or negatives

Camera: MX Film: Fuji Sensia ISO: 100

Camera: K2DMD Film: Kodak T-Max ISO: 400

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