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Sony Batis 18mm F2.8 — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published JP2016-188967A optical prescription (11 elements in 10 groups, 8 aspherical) with a 6.4 mm entrance pupil and 0.25 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | JP2016-188967A · 11 elements in 10 groups (8 aspherical) | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 6.4 mm (at f/2.8) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 65% at f/2.8 (≥86% from f/4) · -1.2 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 92° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 0.76 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 17.4 mm (-3.4%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 47 cm (59 cm – 1.06 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 0.25 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Sony Batis 18mm F2.8 produce?
Wide open at f/2.8, the Sony Batis 18mm F2.8 has a 6.4 mm entrance pupil (18 mm ÷ 2.8) and 65% bokeh roundness in the 90% corner (-1.2 EV corner falloff, reaching ≥86% roundness from f/4). In an upper-body portrait at 0.76 m, the sharp depth-of-field zone spans 47 cm (59 cm to 1.06 m) with a 92° horizontal background angle of view.
Does the Sony Batis 18mm F2.8 show focus breathing at portrait distance?
Based on patent JP2016-188967A, tracing the focusing group at 0.76 m gives an effective framing focal length of 17.4 mm (-3.4% vs. the nominal 18 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Sony Batis 18mm F2.8?
The patent prescription (JP2016-188967A) specifies 11 lens elements in 10 groups with 8 aspherical surfaces. The interactive Optical X-Ray above traces rays through every surface in real time.
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Compare with similar portrait lenses
- Nikon 18mm f/2.8D FX
- Nikon 20mm f/2.8 AI-s
- Nikon 18mm f/4 AI-s
- Canon 20mm f/2.8 USM
- Nikon 16mm f/2.8 AI-s Fisheye
- Nikon 24mm f/3.5 PC-E FX
Also see: depth of field, bokeh, crop factor, lens compression.