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Sigma 85mm F1.2 DG | Art — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published JP 2025-124346 A optical prescription (17 elements in 12 groups, 4 aspherical) with a 70.8 mm entrance pupil and 0.84 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | JP 2025-124346 A · 17 elements in 12 groups (4 aspherical) | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 70.8 mm (at f/1.2) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 70% 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) | 24° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 3.41 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 83.0 mm (-2.4%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 17 cm (3.33 m – 3.49 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 0.84 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Sigma 85mm F1.2 DG | Art produce?
Wide open at f/1.2, the Sigma 85mm F1.2 DG | Art has a 70.8 mm entrance pupil (85 mm ÷ 1.2) and 70% bokeh roundness in the 90% corner (-0.6 EV corner falloff, reaching ≥86% roundness from f/1.8). In an upper-body portrait at 3.41 m, the sharp depth-of-field zone spans 17 cm (3.33 m to 3.49 m) with a 24° horizontal background angle of view.
Does the Sigma 85mm F1.2 DG | Art show focus breathing at portrait distance?
Based on patent JP 2025-124346 A, tracing the focusing group at 3.41 m gives an effective framing focal length of 83.0 mm (-2.4% vs. the nominal 85 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Sigma 85mm F1.2 DG | Art?
The patent prescription (JP 2025-124346 A) specifies 17 lens elements in 12 groups with 4 aspherical surfaces. The interactive Optical X-Ray above traces rays through every surface in real time.
Related comparisons
- Sigma 85mm F1.4 DG DN | Art
- Sigma 85mm F1.4 DG HSM | Art
- Sigma 105mm F1.4 DG HSM | Art
- 35mm vs 85mm focal length comparison
- 40mm vs 85mm focal length comparison
- 50mm vs 85mm focal length comparison
Compare with similar portrait lenses
- Nikon NIKKOR Z 85mm f/1.2 S
- Canon RF 85mm F1.2 L USM
- Canon RF 85mm F1.2 L USM DS
- Sony FE 85mm F1.4 GM II
- Sony FE 85mm F1.4 GM
- Nikon 105mm f/1.4 FX
Also see: depth of field, bokeh, crop factor, lens compression.