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Nikon 28mm f/2.8 AI-s — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US5917663A optical prescription (8 elements in 8 groups) with a 10.0 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 | US5917663A · 8 elements in 8 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 10.0 mm (at f/2.8) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 58% at f/2.8 (≥86% from f/5.6) · -1.1 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 66° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 1.15 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 27.9 mm (-0.4%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 42 cm (97 cm – 1.40 m) | 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 28mm f/2.8 AI-s produce?
Wide open at f/2.8, the Nikon 28mm f/2.8 AI-s has a 10.0 mm entrance pupil (28 mm ÷ 2.8) and 58% bokeh roundness in the 90% corner (-1.1 EV corner falloff, reaching ≥86% roundness from f/5.6). In an upper-body portrait at 1.15 m, the sharp depth-of-field zone spans 42 cm (97 cm to 1.40 m) with a 66° horizontal background angle of view.
Does the Nikon 28mm f/2.8 AI-s show focus breathing at portrait distance?
Based on patent US5917663A, tracing the focusing group at 1.15 m gives an effective framing focal length of 27.9 mm (-0.4% vs. the nominal 28 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Nikon 28mm f/2.8 AI-s?
The patent prescription (US5917663A) specifies 8 lens elements in 8 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Nikon 28mm f/1.4E FX
- Nikon AF 28mm f/1.4D
- Nikon 28mm f/2.0
- Nikon AF 28mm f/2.8D
- Nikon 28mm f/3.5
- Nikon 24mm f/1.4G FX
Compare with similar portrait lenses
- Nikon NIKKOR Z 28mm f/2.8
- Canon RF 28mm F2.8 STM
- Leica Elmarit-M 28mm f/2.8 ASPH.
- Nikon NIKKOR Z 20mm f/1.8 S
Also see: depth of field, bokeh, crop factor, lens compression.