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Matching lenses from each maker's lineup, plus some classic medium and large format lenses. Email me if something is wrong or missing.
Canon FD 55mm f/1.2 S.S.C. Aspherical — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US4364644A optical prescription (8 elements in 6 groups, 1 aspherical) with a 45.8 mm entrance pupil and 0.5 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | US4364644A · 8 elements in 6 groups (1 aspherical) | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 45.8 mm (at f/1.2) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 73% at f/1.2 (≥86% from f/1.8) · -0.6 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 36° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 2.21 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 54.9 mm (-0.2%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 17 cm (2.13 m – 2.30 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 0.5 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Canon FD 55mm f/1.2 S.S.C. Aspherical produce?
Wide open at f/1.2, the Canon FD 55mm f/1.2 S.S.C. Aspherical has a 45.8 mm entrance pupil (55 mm ÷ 1.2) and 73% bokeh roundness in the 90% corner (-0.6 EV corner falloff, reaching ≥86% roundness from f/1.8). In an upper-body portrait at 2.21 m, the sharp depth-of-field zone spans 17 cm (2.13 m to 2.30 m) with a 36° horizontal background angle of view.
Does the Canon FD 55mm f/1.2 S.S.C. Aspherical show focus breathing at portrait distance?
Based on patent US4364644A, tracing the focusing group at 2.21 m gives an effective framing focal length of 54.9 mm (-0.2% vs. the nominal 55 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Canon FD 55mm f/1.2 S.S.C. Aspherical?
The patent prescription (US4364644A) specifies 8 lens elements in 6 groups with 1 aspherical surfaces. The interactive Optical X-Ray above traces rays through every surface in real time.
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Compare with similar portrait lenses
- Nikon 55mm f/1.2 AI
- Nikon 58mm f/1.2 Noct-NIKKOR
- Sony FE 50mm F1.2 GM
- Canon RF 50mm F1.2 L USM
- Nikon NIKKOR Z 50mm f/1.2 S
- Canon 85mm f/1.8
Also see: depth of field, bokeh, crop factor, lens compression.