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Leica APO-Summicron-M 50mm f/2 ASPH. — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US4123144A optical prescription (6 elements in 4 groups) with a 25.0 mm entrance pupil and 0.7 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | US4123144A · 6 elements in 4 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 25.0 mm (at f/2) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 91% at f/2 · -0.3 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 39° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 2.01 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 50.6 mm (+1.3%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 29 cm (1.88 m – 2.17 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 0.7 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Leica APO-Summicron-M 50mm f/2 ASPH. produce?
Wide open at f/2, the Leica APO-Summicron-M 50mm f/2 ASPH. has a 25.0 mm entrance pupil (50 mm ÷ 2) and 91% bokeh roundness in the 90% corner (-0.3 EV corner falloff). In an upper-body portrait at 2.01 m, the sharp depth-of-field zone spans 29 cm (1.88 m to 2.17 m) with a 39° horizontal background angle of view.
Does the Leica APO-Summicron-M 50mm f/2 ASPH. show focus breathing at portrait distance?
Based on patent US4123144A, tracing the focusing group at 2.01 m gives an effective framing focal length of 50.6 mm (+1.3% vs. the nominal 50 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Leica APO-Summicron-M 50mm f/2 ASPH.?
The patent prescription (US4123144A) specifies 6 lens elements in 4 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Leica APO-Summicron-M 50mm f/2 ASPH. vs. Leica Summicron-M 50mm f/2
- Leica APO-Summicron-M 50mm f/2 ASPH. vs. Leica Summilux-M 50mm f/1.4
- Leica APO-Summicron-M 50mm f/2 ASPH. vs. Leica Noctilux-M 50mm f/0.95 ASPH.
- Leica Noctilux-M 50mm f/0.95 ASPH.
- Leica Summilux-M 50mm f/1.4
- Leica Summicron-M 50mm f/2
Compare with similar portrait lenses
- Sony MD 50mm F2
- Nikon 50mm f/2
- Leica APO-Summicron-SL 50mm f/2 ASPH.
- Sony FE 50mm F1.8
- Sony Distagon FE 35mm F1.4 ZA
Also see: depth of field, bokeh, crop factor, lens compression.