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Nikon NIKKOR Z 20mm f/1.8 S — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published WO2021117429A1 optical prescription (15 elements in 11 groups, 5 aspherical) with a 11.1 mm entrance pupil and 0.2 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | WO2021117429A1 · 15 elements in 11 groups (5 aspherical) | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 11.1 mm (at f/1.8) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 63% at f/1.8 (≥86% from f/2.8) · -1.2 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 85° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 0.84 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 19.7 mm (-1.3%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 28 cm (72 cm – 100 cm) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 0.2 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Nikon NIKKOR Z 20mm f/1.8 S produce?
Wide open at f/1.8, the Nikon NIKKOR Z 20mm f/1.8 S has a 11.1 mm entrance pupil (20 mm ÷ 1.8) and 63% bokeh roundness in the 90% corner (-1.2 EV corner falloff, reaching ≥86% roundness from f/2.8). In an upper-body portrait at 0.84 m, the sharp depth-of-field zone spans 28 cm (72 cm to 100 cm) with a 85° horizontal background angle of view.
Does the Nikon NIKKOR Z 20mm f/1.8 S show focus breathing at portrait distance?
Based on patent WO2021117429A1, tracing the focusing group at 0.84 m gives an effective framing focal length of 19.7 mm (-1.3% vs. the nominal 20 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Nikon NIKKOR Z 20mm f/1.8 S?
The patent prescription (WO2021117429A1) specifies 15 lens elements in 11 groups with 5 aspherical surfaces. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Nikon NIKKOR Z 20mm f/1.8 S vs. Nikon NIKKOR Z 24mm f/1.8 S
- Nikon NIKKOR Z 24mm f/1.8 S
- 24mm vs 35mm focal length comparison
- 24mm vs 50mm focal length comparison
- 28mm vs 35mm focal length comparison
- 28mm vs 50mm focal length comparison
Compare with similar portrait lenses
- Nikon AF-S 20mm f/1.8G ED
- Sony FE 20mm F1.8 G
- Canon RF 20mm F1.4 L VCM
- Nikon 20mm f/2.8 AI-s
- Canon 20mm f/2.8 USM
- Nikon 24mm f/2.0 AI-s
Also see: depth of field, bokeh, crop factor, lens compression.