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Leica Super-Elmar-M 21mm f/3.4 ASPH. — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US3512874A optical prescription (10 elements in 8 groups) with a 6.2 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 | US3512874A · 10 elements in 8 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 6.2 mm (at f/3.4) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 62% at f/3.4 · -1.2 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 82° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 0.87 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 20.6 mm (-1.8%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 56 cm (68 cm – 1.24 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 Super-Elmar-M 21mm f/3.4 ASPH. produce?
Wide open at f/3.4, the Leica Super-Elmar-M 21mm f/3.4 ASPH. has a 6.2 mm entrance pupil (21 mm ÷ 3.4) and 62% bokeh roundness in the 90% corner (-1.2 EV corner falloff). In an upper-body portrait at 0.87 m, the sharp depth-of-field zone spans 56 cm (68 cm to 1.24 m) with a 82° horizontal background angle of view.
Does the Leica Super-Elmar-M 21mm f/3.4 ASPH. show focus breathing at portrait distance?
Based on patent US3512874A, tracing the focusing group at 0.87 m gives an effective framing focal length of 20.6 mm (-1.8% vs. the nominal 21 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Leica Super-Elmar-M 21mm f/3.4 ASPH.?
The patent prescription (US3512874A) specifies 10 lens elements in 8 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Leica ELMARIT-M 24mm f/2.8 ASPH
- Leica SUPER-ELMAR-M 18mm f/3.8 ASPH
- 24mm vs 35mm focal length comparison
- 24mm vs 50mm focal length comparison
- 28mm vs 35mm focal length comparison
- 28mm vs 50mm focal length comparison
Compare with similar portrait lenses
- Nikon Nikkor-O 2.1cm f/4
- Nikon 20mm f/4 AI
- Nikon 20mm f/2.8 AI-s
- Canon 20mm f/2.8 USM
- Nikon 24mm f/3.5 PC-E FX
- Nikon 16mm f/2.8 AI-s Fisheye
Also see: depth of field, bokeh, crop factor, lens compression.