Carl Zeiss Carl Zeiss Flektogon 20mm f2.8 Heritage

Overview

The Carl Zeiss Flektogon 20mm f2.8 is a superwide-angle lens produced in M42 screw mount by Carl Zeiss Jena in the former East Germany (DDR). One reviewer's copy was made in 1976, and had it CLA'd by a specialist firm (Foto-Service Olbrich) located in Görlitz, Germany, near Jena — underscoring the lens's deep East German roots. It was developed as a distortion-corrected superwide, a design goal one long-time user explicitly sought: a superwide with easily corrected (indeed nearly negligible) distortion. The lens is prized as a robust, all-metal-and-glass optic that adapts easily to any modern mirrorless system via M42. It exists alongside a slower Flektogon 20mm f4 sibling, and reviewers consider the f2.8 the better lens — notably sharper wide open. No established nicknames are evidenced in the reviews. The cult following stems from its exceptional distortion control, saturated color rendering, and its strong wide-open performance that makes it especially recommended for astrophotography.

Verdict: The Carl Zeiss Flektogon 20mm f2.8 is a superwide for photographers who prioritize distortion-free geometry and saturated color — making it excellent for architecture and landscape — while its strong wide-open sharpness makes it a standout choice for astrophotography. If you don't need f2.8 and shoot mostly stopped down on a tripod, the cheaper f4 sibling is nearly its equal; but for wide-open work, the f2.8 is clearly the better lens.

Optical Character

Bokeh

Rated moderate by the community (~6.8/10); not primarily a bokeh lens with no evidence of bubbles or swirl.

Color

Saturated, fine colors as described by multiple reviewers.

Sharpness wide open

Sharp even wide open at f2.8, better than the f4 version across apertures, with good corner and distant-subject sharpness.

Flare resistance

Reviewer notes no cons when a lens hood is used, implying a hood is beneficial for controlling flare.

Vignetting

Present wide open at f2.8 but almost gone when stopped down to f4.

Community Insights

What people love

Near-total absence of distortion — straight lines render nearly straight all the way to the outer corners, ideal for architecture and composition
Saturated, fine color rendering and strong general photo quality
Excellent sharpness wide open at f2.8, making it well suited for astrophotography
Robust, essentially indestructible all-metal-and-glass build
Easy M42 adaptation to virtually any modern camera system (Sony, Canon, Nikon, Fuji, Pentax, etc.)
Superior to the f4 sibling wide open and across most apertures

What people dislike

Vignetting wide open at f2.8 (though it clears up by f4)
Marginally outperformed by the f4 version at f16
Aging copies may have issues like beyond-infinity focus marking or damaged filter threads requiring a CLA/restoration
Costs roughly 100€ more than the f4 version

Pro Tips

Use a lens hood — one reviewer states the lens has no cons when a hood is used
For astrophotography, shoot wide open at f2.8 where this version notably outperforms the f4 sibling
Stop down to f4 to nearly eliminate vignetting
For landscape/architecture on a tripod, f8 gives excellent results with no meaningful advantage over the slower f4 sibling
Consider buying a professionally CLA'd copy to resolve infinity and filter-thread issues

Sources (1)

Web-grounded synthesissecondary

The Carl Zeiss Flektogon 20mm f2.8 is a superwide-angle lens produced in M42 screw mount by Carl Zeiss Jena in the former East Germany (DDR). One reviewer's copy was made in 1976, and had it CLA'd by a specialist firm (Foto-Service Olbrich) located in Görlitz, Germany, near Jena — underscoring the lens's deep East German roots. It was developed as a distortion-corrected superwide, a design goal one long-time user explicitly sought: a superwide with easily corrected (indeed nearly negligible) distortion. The lens is prized as a robust, all-metal-and-glass optic that adapts easily to any modern mirrorless system via M42. It exists alongside a slower Flektogon 20mm f4 sibling, and reviewers consider the f2.8 the better lens — notably sharper wide open. No established nicknames are evidenced in the reviews. The cult following stems from its exceptional distortion control, saturated color rendering, and its strong wide-open performance that makes it especially recommended for astrophotography.

https://www.pentaxforums.com/userreviews/carl-zeiss-20mm-f2-8-flektogon-mc.htmlhttp://digitalvintagelens.com/2017/10/19/vergleich-carl-zeiss-flektogon-20mm-f28-und-carl-zeiss-flektogon-20mm-f4/