Sigma Sigma 28mm f2.8 Heritage

Overview

The Sigma 28mm f/2.8 in question is the Mini-Wide II, a compact manual-focus wide-angle prime that Sigma produced across the 1980s and early 1990s. It was offered in Pentax K-mount (in both P-KA and P-KM variants), M42, and other popular mounts of the era, targeting 35mm SLR shooters looking for an affordable wide-angle option. The lens was also rebranded and sold under the Promaster Spectrum name, making it a common find on the used market. According to the review database, some later K-mount versions include an 'A' setting for aperture automation on compatible Pentax bodies, though functionality may vary. Its appeal lies in being a budget-friendly, character-rich alternative to Pentax's own OEM 28mm primes. With a 97% recommendation rate among reviewers and an average price of around $41, it has developed a modest cult following as a cheap way to get a usable vintage wide-angle with a 'slightly vintage character.' No specific community nickname is evidenced beyond the 'Mini-Wide' family branding itself.

Verdict: The Sigma Mini-Wide II 28mm f/2.8 is a compact, affordable manual-focus wide-angle that delivers sharp centers from f/4–f/8 and a pleasing, slightly vintage character. It won't out-resolve Pentax's OEM 28mm primes, but for street, landscape, and close-up shooters seeking a characterful and inexpensive lens — whether native on Pentax DSLRs or adapted to mirrorless — it offers excellent value and earns its 97% recommendation.

Optical Character

Bokeh

Respectable but not a standout, rated 7.7 on average with no notable swirl or bubbles.

Sharpness wide open

Sharp in the center from f/4 to f/8, with corner performance undetailed.

Contrast

Decent contrast with a slightly vintage character, not as refined as OEM Pentax 28mm primes.

Community Insights

What people love

Excellent value — an average price around $41 with a 97% recommendation rate makes it an affordable entry into vintage wide-angle shooting.
Sharp center rendering from f/4 to f/8, earning a high 8.6 sharpness rating.
Compact and lightweight at around 210g, making it easy to carry for street and travel use.
Smooth focus throw (~200°) that aids precise manual focusing (handling rated 8.7).
Close-focus ability down to 22cm (1:4.5 magnification) for tight framing and environmental close-ups.
Native K-mount fit on Pentax DSLRs and easy adaptation to mirrorless systems like Sony E, Canon RF, and Micro Four Thirds.

What people dislike

Not as optically refined as Pentax's own OEM 28mm primes.
The 'A' aperture automation setting on some versions may not function reliably on all bodies (functionality may vary).

Pro Tips

Stop down to between f/4 and f/8 for the sharpest center results.
Take advantage of the 22cm close-focus distance for environmental detail and close-up shots.
Use the long ~200° focus throw for careful, precise manual focusing.
Adapt it to mirrorless bodies (Sony E, Canon RF, MFT) if you want easy focus confirmation and to enjoy its vintage character.

Sources (1)

Web-grounded synthesissecondary

The Sigma 28mm f/2.8 in question is the Mini-Wide II, a compact manual-focus wide-angle prime that Sigma produced across the 1980s and early 1990s. It was offered in Pentax K-mount (in both P-KA and P-KM variants), M42, and other popular mounts of the era, targeting 35mm SLR shooters looking for an affordable wide-angle option. The lens was also rebranded and sold under the Promaster Spectrum name, making it a common find on the used market. According to the review database, some later K-mount versions include an 'A' setting for aperture automation on compatible Pentax bodies, though functionality may vary. Its appeal lies in being a budget-friendly, character-rich alternative to Pentax's own OEM 28mm primes. With a 97% recommendation rate among reviewers and an average price of around $41, it has developed a modest cult following as a cheap way to get a usable vintage wide-angle with a 'slightly vintage character.' No specific community nickname is evidenced beyond the 'Mini-Wide' family branding itself.

https://www.pentaxforums.com/userreviews/sigma-28mm-f2-8-mini-wide-ii.html