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Canon 400mm f/5.6 L — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published JP2018-180209A optical prescription (7 elements in 6 groups) with a 71.4 mm entrance pupil and 3.5 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | JP2018-180209A · 7 elements in 6 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 71.4 mm (at f/5.6) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 88% at f/5.6 · -0.2 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 5° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 15.99 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 425.3 mm (+6.3%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 79 cm (16 m – 16 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 3.5 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Canon 400mm f/5.6 L produce?
Wide open at f/5.6, the Canon 400mm f/5.6 L has a 71.4 mm entrance pupil (400 mm ÷ 5.6) and 88% bokeh roundness in the 90% corner (-0.2 EV corner falloff). In an upper-body portrait at 15.99 m, the sharp depth-of-field zone spans 79 cm (16 m to 16 m) with a 5° horizontal background angle of view.
Does the Canon 400mm f/5.6 L show focus breathing at portrait distance?
Based on patent JP2018-180209A, tracing the focusing group at 15.99 m gives an effective framing focal length of 425.3 mm (+6.3% vs. the nominal 400 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Canon 400mm f/5.6 L?
The patent prescription (JP2018-180209A) specifies 7 lens elements in 6 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
Compare with similar portrait lenses
- Leica Telyt 400mm f/5
- Canon RF 400mm F2.8 L IS USM
- Nikon NIKKOR Z 400mm f/2.8 TC VR S
- Nikon 300mm f/4.5 ED-IF AI-s
Also see: depth of field, bokeh, crop factor, lens compression.