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Canon RF 45mm F1.2 STM — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US20260194735A1 optical prescription (9 elements in 7 groups, 2 aspherical) with a 37.5 mm entrance pupil and 0.4 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | US20260194735A1 · 9 elements in 7 groups (2 aspherical) | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 37.5 mm (at f/1.2) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 46% at f/1.2 (≥86% from f/2.8) · -1.4 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 44° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 1.82 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 44.2 mm (-1.8%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 17 cm (1.73 m – 1.91 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 0.4 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Canon RF 45mm F1.2 STM produce?
Wide open at f/1.2, the Canon RF 45mm F1.2 STM has a 37.5 mm entrance pupil (45 mm ÷ 1.2) and 46% bokeh roundness in the 90% corner (-1.4 EV corner falloff, reaching ≥86% roundness from f/2.8). In an upper-body portrait at 1.82 m, the sharp depth-of-field zone spans 17 cm (1.73 m to 1.91 m) with a 44° horizontal background angle of view.
Does the Canon RF 45mm F1.2 STM show focus breathing at portrait distance?
Based on patent US20260194735A1, tracing the focusing group at 1.82 m gives an effective framing focal length of 44.2 mm (-1.8% vs. the nominal 45 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Canon RF 45mm F1.2 STM?
The patent prescription (US20260194735A1) specifies 9 lens elements in 7 groups with 2 aspherical surfaces. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Canon RF 45mm F1.2 STM vs. Canon RF 50mm F1.2 L USM
- Canon RF 45mm F1.2 STM vs. Canon RF 50mm F1.8 STM
- Canon RF 50mm F1.2 L USM
- Canon RF 50mm F1.4 L VCM
- Canon RF 50mm F1.8 STM
- Canon RF 35mm F1.4 L VCM
Compare with similar portrait lenses
- Sony FE 50mm F1.2 GM
- Nikon NIKKOR Z 50mm f/1.2 S
- Leica NOCTILUX 50mm f/1.2 ASPH
- Sony FE 50mm F1.4 GM
- Nikon 58mm f/1.4 G FX
Also see: depth of field, bokeh, crop factor, lens compression.