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Canon RF 20mm F1.4 L VCM — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US20250389929A1 optical prescription (16 elements in 11 groups, 3 aspherical) with a 14.3 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 | US20250389929A1 · 16 elements in 11 groups (3 aspherical) | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 14.3 mm (at f/1.4) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 43% at f/1.4 (≥86% from f/4) · -1.9 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 88° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 0.84 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 18.6 mm (-6.9%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 22 cm (74 cm – 96 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 RF 20mm F1.4 L VCM produce?
Wide open at f/1.4, the Canon RF 20mm F1.4 L VCM has a 14.3 mm entrance pupil (20 mm ÷ 1.4) and 43% bokeh roundness in the 90% corner (-1.9 EV corner falloff, reaching ≥86% roundness from f/4). In an upper-body portrait at 0.84 m, the sharp depth-of-field zone spans 22 cm (74 cm to 96 cm) with a 88° horizontal background angle of view.
Does the Canon RF 20mm F1.4 L VCM show focus breathing at portrait distance?
Based on patent US20250389929A1, tracing the focusing group at 0.84 m gives an effective framing focal length of 18.6 mm (-6.9% vs. the nominal 20 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Canon RF 20mm F1.4 L VCM?
The patent prescription (US20250389929A1) specifies 16 lens elements in 11 groups with 3 aspherical surfaces. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Canon RF 20mm F1.4 L VCM vs. Canon RF 24mm F1.4 L VCM
- Canon RF 20mm F1.4 L VCM vs. Canon RF 14mm F1.4 L VCM
- Canon RF 24mm F1.4 L VCM
- Canon RF 24mm F1.8 MACRO IS STM
- Canon RF 16mm F2.8 STM
Compare with similar portrait lenses
- Sony FE 20mm F1.8 G
- Nikon NIKKOR Z 20mm f/1.8 S
- Nikon AF-S 20mm f/1.8G ED
- Canon 20mm f/2.8 USM
- Nikon 20mm f/2.8 AI-s
- Sony FE 28mm F2
Also see: depth of field, bokeh, crop factor, lens compression.