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Canon 15mm f/2.8 Fisheye — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published JP S63-017421A optical prescription (8 elements in 7 groups) with a 5.4 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 | JP S63-017421A · 8 elements in 7 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 5.4 mm (at f/2.8) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 35% at f/2.8 · -4.1 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 127° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 0.64 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 9.0 mm (-40.0%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 51 cm (48 cm – 99 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 Canon 15mm f/2.8 Fisheye produce?
Wide open at f/2.8, the Canon 15mm f/2.8 Fisheye has a 5.4 mm entrance pupil (15 mm ÷ 2.8) and 35% bokeh roundness in the 90% corner (-4.1 EV corner falloff). In an upper-body portrait at 0.64 m, the sharp depth-of-field zone spans 51 cm (48 cm to 99 cm) with a 127° horizontal background angle of view.
Does the Canon 15mm f/2.8 Fisheye show focus breathing at portrait distance?
Based on patent JP S63-017421A, tracing the focusing group at 0.64 m gives an effective framing focal length of 9.0 mm (-40.0% vs. the nominal 15 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Canon 15mm f/2.8 Fisheye?
The patent prescription (JP S63-017421A) specifies 8 lens elements in 7 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Canon 14mm f/2.8 L II
- 24mm vs 35mm focal length comparison
- 24mm vs 50mm focal length comparison
- 28mm vs 35mm focal length comparison
- 28mm vs 50mm focal length comparison
- 23mm APS-C vs 35mm full frame focal length comparison
Compare with similar portrait lenses
- Canon RF 16mm F2.8 STM
- Nikon 16mm f/2.8 AI-s Fisheye
- Sony FE 14mm F1.8 GM
- Fujifilm XF 16mm F2.8 R WR
- Nikon Nikkor-O 2.1cm f/4
Also see: depth of field, bokeh, crop factor, lens compression.