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Canon 500mm f/4 L IS — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US6115188A optical prescription (16 elements in 12 groups) with a 125.0 mm entrance pupil and 4.5 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | US6115188A · 16 elements in 12 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 125.0 mm (at f/4) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 74% at f/4 (≥86% from f/5.6) · -0.5 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 4° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 19.99 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 546.3 mm (+9.3%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 56 cm (20 m – 20 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 4.5 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Canon 500mm f/4 L IS produce?
Wide open at f/4, the Canon 500mm f/4 L IS has a 125.0 mm entrance pupil (500 mm ÷ 4) and 74% bokeh roundness in the 90% corner (-0.5 EV corner falloff, reaching ≥86% roundness from f/5.6). In an upper-body portrait at 19.99 m, the sharp depth-of-field zone spans 56 cm (20 m to 20 m) with a 4° horizontal background angle of view.
Does the Canon 500mm f/4 L IS show focus breathing at portrait distance?
Based on patent US6115188A, tracing the focusing group at 19.99 m gives an effective framing focal length of 546.3 mm (+9.3% vs. the nominal 500 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Canon 500mm f/4 L IS?
The patent prescription (US6115188A) specifies 16 lens elements in 12 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Canon 400mm f/2.8 L IS
- Canon 600mm f/4 L IS
- Canon 400mm f/5.6 L
- 50mm vs 200mm focal length comparison
- 70mm vs 200mm focal length comparison
- 85mm vs 200mm focal length comparison
Compare with similar portrait lenses
- Nikon AF-S 500mm f/4E FL ED VR
- Fujifilm GF 500mm F5.6 R LM OIS WR
- Canon RF 400mm F2.8 L IS USM
- Nikon NIKKOR Z 400mm f/2.8 TC VR S
Also see: depth of field, bokeh, crop factor, lens compression.