Production
-
Country
East Germany (GDR)
Optical
Retrofocus (reverse-telephoto) wide-angle Flektogon design.
Updated
Jul 15, 2026
Carl Zeiss Carl Zeiss Flektogon 20mm f2.8
M42 · 20mm · f/2.8
Compiled from 1 real reviews · AI-assisted · accuracy-checked · Updated 15 Jul 2026
Overview
The Carl Zeiss Flektogon 20mm f2.8 is a superwide-angle from Carl Zeiss Jena, made in the DDR (East Germany, the reviews explicitly identify it as 'Carl Zeiss Jena DDR Flektogon'), the successor to the earlier f4 version. The 'Flektogon' name marks it as a retrofocus (reverse-telephoto) wide-angle design, which is what allowed such a wide field of view to clear an SLR mirror on the M42 screw mount. One reviewer's copy was manufactured in 1976, placing it firmly in the classic Jena era of all-metal-and-glass construction that reviewers describe as 'almost indestructible.' It earned a devoted following among adapted-lens shooters for two reasons the reviews make plain: it is exceptionally well-corrected for distortion for such a wide focal length (a rarity that made photographers hunt specifically for it), and it is strikingly sharp even wide open at f2.8 — sharp enough that one reviewer recommends it over the slower f4 sibling specifically for astrophotography. No established nickname or jargon term for this lens appears in the provided reviews, so none is asserted here.
Verdict: A precision superwide for photographers who value optical correctness over character effects: near-distortion-free geometry, saturated colour, and biting sharpness that holds even wide open. It's the pick for landscape, architecture, and especially astrophotography — anyone who needs a trustworthy 20mm that performs at f2.8. Bokeh chasers and those wanting swirl or glow should look elsewhere; if you mostly shoot stopped down on a tripod, the cheaper f4 sibling nearly matches it, so the f2.8 earns its premium chiefly for its wide-open ability.
Optical Character
Bokeh
Only moderately rated; acceptable but not standout out-of-focus rendering with no swirl, bubbles, or glow.
Color
Saturated yet faithful rendering, described as 'fine' and rich colours.
Sharpness wide open
Sharp even wide open at f2.8 including corners, holding through the range, with f8 a sweet spot.
Flare resistance
Susceptible to veiling glare into strong light; a lens hood is needed to preserve contrast.
Contrast
Good contrast best preserved with a hood, though not quantified by reviewers.
Vignetting
Present wide open but largely cleared by stopping down to f4.
Community Insights
What people love
- Extremely low distortion for a superwide — straight lines stay straight to the corners, making architecture and landscape composition trustworthy and easy.
- Sharp wide open at f2.8, including corners and distant detail, and sharper wide open than the slower f4 version — which makes it a favourite for astrophotography.
- Saturated, pleasing colour rendering.
- Robust, all-metal-and-glass Jena build described as almost indestructible.
- Very close minimum focus (0.19 m) for dramatic near-foreground wide-angle shots.
- Consistently recommended — 100% of database reviewers recommend it.
What people dislike
- Needs a lens hood to control flare/veiling glare when shooting toward the light — without one, contrast suffers.
- Some vignetting wide open until stopped down to about f4.
- By f8–f16 its sharpness advantage over the cheaper f4 version disappears (at f16 the f4 can even edge ahead), so the price premium only pays off for wide-open use.
- Older copies may need servicing — one reviewer's example arrived with an off 'infinity' mark and a damaged filter thread requiring professional restoration.
- Commands a noticeable price premium over the f4 sibling.
Pro Tips
- Always fit a lens hood — reviewers single this out as the fix that eliminates the lens's only real weakness (flare/veiling glare into strong light).
- For astrophotography and low light, shoot it wide open at f2.8; this is where it most outperforms the f4 version, with usable corners and detail.
- If wide-open vignetting bothers you, stop down to f4 to largely clear it.
- For maximum landscape/architecture sharpness across the frame, f8 is a sweet spot — beyond it you gain little.
- Exploit the very close 0.19 m minimum focus to place a strong near-foreground element while keeping the wide background in play.
- Trust its geometry: because distortion is minimal to the corners, you can place horizons and straight lines near the frame edge without correction.
- Verify and, if needed, recalibrate infinity focus on your copy before critical wide-open or astro work.
Compatible Adapters
Real adapters from our shop that fit this lens mount.
Standard · ฿325 · In stock
Standard · ฿325 · In stock
Standard · ฿325 · In stock
Standard · ฿325 · In stock
Standard · ฿540 · In stock
Standard · ฿540 · In stock
Standard · ฿540 · In stock
Standard · ฿540 · In stock
Standard · ฿540 · In stock
Standard · ฿1,250 · In stock
Standard · ฿890 · Out of stock
Standard · ฿890 · Out of stock
Sources (1)
Web research
A precision superwide for photographers who value optical correctness over character effects: near-distortion-free geometry, saturated colour, and biting sharpness that holds even wide open. It's the pick for landscape, architecture, and especially astrophotography — anyone who needs a trustworthy 20mm that performs at f2.8. Bokeh chasers and those wanting swirl or glow should look elsewhere; if you mostly shoot stopped down on a tripod, the cheaper f4 sibling nearly matches it, so the f2.8 earns its premium chiefly for its wide-open ability.
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/