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Kodak Aero Ektar 178mm f/2.5 — Bokeh & Optical Ray-Tracing Simulator
Interactive 3D portrait ray-traced through the published US2343627A optical prescription (7 elements in 4 groups) with a 71.2 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 | US2343627A · 7 elements in 4 groups | Traced surface by surface in WebGL2 |
| Entrance Pupil Diameter | 71.2 mm (at f/2.5) | Controls distant background blur disc size |
| Corner Bokeh Roundness (90% Field) | 89% at f/2.5 · -0.3 EV | Mechanical vignetting (cat’s-eye vs. round corner highlights) |
| Background Field of View (Compression) | 35° horizontal | Width of the background room visible behind the subject |
| Upper-Body Working Distance | 2.13 m | Camera-to-subject distance for head-to-waist framing |
| Effective Focal Length (Breathing) | 193.3 mm (+8.6%) | Actual framing focal length at portrait distance |
| Depth of Field (Sharp Zone) | 9.9 cm (2.08 m – 2.18 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 Kodak Aero Ektar 178mm f/2.5 produce?
Wide open at f/2.5, the Kodak Aero Ektar 178mm f/2.5 has a 71.2 mm entrance pupil (178 mm ÷ 2.5) and 89% bokeh roundness in the 90% corner (-0.3 EV corner falloff). In an upper-body portrait at 2.13 m, the sharp depth-of-field zone spans 9.9 cm (2.08 m to 2.18 m) with a 35° horizontal background angle of view.
Does the Kodak Aero Ektar 178mm f/2.5 show focus breathing at portrait distance?
Based on patent US2343627A, tracing the focusing group at 2.13 m gives an effective framing focal length of 193.3 mm (+8.6% vs. the nominal 178 mm). You can toggle "Match subject size" in the simulator to see the framing shift live.
What optical design is inside the Kodak Aero Ektar 178mm f/2.5?
The patent prescription (US2343627A) specifies 7 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 180mm f/2.8 AI
- Canon 180mm f/3.5 L Macro
- Nikon 200mm f/2 VR II FX
- Canon 200mm f/2L IS USM
- Canon EF 200mm f/1.8 L USM
- Sony FE 135mm F1.8 GM
Also see: depth of field, bokeh, crop factor, lens compression.