Specifications#
- Brand
- Zeiss
- Model
- Carl Zeiss Jena Flektogon 20mm f/4
- Lens type
- Ultra-wide prime
- Focal length
- 20 mm
- Maximum aperture
- f/4
- Image circle
- Full frame (36×24 mm)
- Mount(s)
- M42 screw mount
- Projection
- Rectilinear
- Lensfun correction profile
- Yes — distortion/vignetting/TCA
Equivalent focal length on different cameras#
Field of view and depth-of-field equivalence when this lens is used on bodies with different sensor sizes (natively or via an adapter).
| Camera format | At 20 mm | Equiv. aperture (DoF) |
|---|---|---|
| Full frame | 20 mm · 94° | f/4.0 |
| APS-C | 30 mm · 70° | f/6.0 |
| APS-C (Canon) | 32 mm · 68° | f/6.4 |
| Micro Four Thirds | 40 mm · 57° | f/8.0 |
Depth of field & background blur#
Computed on its native Full frame format (CoC 30 µm). “Blur @2 m” is the size of an out-of-focus point at infinity, as a percentage of frame width, with the subject at 2 m — a simple bokeh index. Full table: 20 mm f/4 on full frame.
| Focal | Aperture | at 1 m | at 2 m | at 5 m | at 10 m | Hyperfocal | Blur @2 m |
|---|---|---|---|---|---|---|---|
| 20 mm | f/4 | 64.4 cm | 3.67 m | ∞ | ∞ | 3.35 m | 0.1% |
| 20 mm | f/8 | 1.80 m | ∞ | ∞ | ∞ | 1.69 m | 0.1% |
Handheld & night-sky limits#
NPF assumes typical 20–24 MP sensors (≈6 µm pixels on full frame, ≈3.9 µm on APS-C, ≈3.3 µm on Micro Four Thirds).
| Body | Min. handheld shutter (longest focal) | 500 rule at 20 mm | NPF at 20 mm, f/4 |
|---|---|---|---|
| Full frame | 1/20 s | 25 s | 16 s |
| APS-C | 1/30 s | 17 s | 13 s |
| APS-C (Canon) | 1/30 s | 16 s | 13 s |
| Micro Four Thirds | 1/40 s | 12 s | 12 s |
Compatible cameras#
Bodies in our database with a native M42 screw mount mount.
Adapt it to other systems#
Frequently asked questions#
Is the Zeiss Carl Zeiss Jena Flektogon 20mm f/4 full frame?
Yes — it covers the full 36 × 24 mm frame.
What is the Zeiss Carl Zeiss Jena Flektogon 20mm f/4 equivalent to on APS-C?
On a 1.5× APS-C body it frames like 30 mm, and like 32 mm on Canon APS-C.
What is the Zeiss Carl Zeiss Jena Flektogon 20mm f/4 good for?
As a ultra-wide prime it suits astrophotography, landscapes and dramatic perspectives.
Sources & licences#
- Lensfun lens database — CC BY-SA 3.0
Last updated October 03, 2026 · How we calculate · Sources