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Leica APO-Telyt-R 280mm f/2.8 — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US5388006A optical prescription (8 elements in 7 groups) with a 100.0 mm entrance pupil and 2.5 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | US5388006A · 8 elements in 7 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 100.0 mm (at f/2.8) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 75% at f/2.8 (≥86% from f/5.6) · -0.5 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 7° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 11.20 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 307.5 mm (+9.8%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 39 cm (11 m – 11 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 2.5 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Leica APO-Telyt-R 280mm f/2.8 produce?
Wide open at f/2.8, the Leica APO-Telyt-R 280mm f/2.8 has a 100.0 mm entrance pupil (280 mm ÷ 2.8) and 75% bokeh roundness in the 90% corner (-0.5 EV corner falloff, reaching ≥86% roundness from f/5.6). In an upper-body portrait at 11.20 m, the sharp depth-of-field zone spans 39 cm (11 m to 11 m) with a 7° horizontal background angle of view.
Does the Leica APO-Telyt-R 280mm f/2.8 show focus breathing at portrait distance?
Based on patent US5388006A, tracing the focusing group at 11.20 m gives an effective framing focal length of 307.5 mm (+9.8% vs. the nominal 280 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Leica APO-Telyt-R 280mm f/2.8?
The patent prescription (US5388006A) specifies 8 lens elements in 7 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
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Compare with similar portrait lenses
- Sony FE 300mm F2.8 GM OSS
- Nikon 300mm f/2.8 AF-S II FX
- Canon 300mm f/2.8 L IS
- Nikon 300mm f/2 ED IF
- Canon 300mm f/4 L IS
- Nikon 200mm f/2 VR II FX
Also see: depth of field, bokeh, crop factor, lens compression.