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Rodenstock Grandagon N 90mm f/4.5 — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published DE2444954A1 optical prescription (8 elements in 4 groups) with a 20.0 mm entrance pupil and 1 m minimum focus.
Optical & Portrait Specifications (Upper Body Framing)
| Optical & Portrait Metric | Measured / Patent Value | What It Means in Practice |
|---|---|---|
| Patent Prescription | DE2444954A1 · 8 elements in 4 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 20.0 mm (at f/4.5) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 98% at f/4.5 · -0.5 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 64° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 1.10 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 97.5 mm (+8.3%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 19 cm (1.01 m – 1.20 m) | Sharp zone at wide-open aperture |
| Minimum Focus Distance | 1 m | Closest focusing distance from the sensor |
Questions
How much background blur and corner cat's-eye does the Rodenstock Grandagon N 90mm f/4.5 produce?
Wide open at f/4.5, the Rodenstock Grandagon N 90mm f/4.5 has a 20.0 mm entrance pupil (90 mm ÷ 4.5) and 98% bokeh roundness in the 90% corner (-0.5 EV corner falloff). In an upper-body portrait at 1.10 m, the sharp depth-of-field zone spans 19 cm (1.01 m to 1.20 m) with a 64° horizontal background angle of view.
Does the Rodenstock Grandagon N 90mm f/4.5 show focus breathing at portrait distance?
Based on patent DE2444954A1, tracing the focusing group at 1.10 m gives an effective framing focal length of 97.5 mm (+8.3% vs. the nominal 90 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Rodenstock Grandagon N 90mm f/4.5?
The patent prescription (DE2444954A1) specifies 8 lens elements in 4 groups. The interactive Optical X-Ray above traces rays through every surface in real time.
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Compare with similar portrait lenses
- Nikon Nikkor SW 90mm f/4.5
- Fujifilm Fujinon SWD 90mm f/5.6
- Leica Macro-Elmar-M 90mm f/4
- Fujifilm Fujinon SW 90mm f/8
- Nikon 85mm f/3.5 VR DX
- Nikon 55mm f/2.8 Micro AI-s
Also see: depth of field, bokeh, crop factor, lens compression.