add per-cu3s README: 2026_03_03_11-31-31_README.md

data/day2/2026_03_03_11-31-31_README.md

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+# 2026_03_03_11-31-31
+
+**Capture date:** 2026-03-03  ·  **Day:** `day2`  ·  **Subfolder timestamp:** `2026_03_03_11-31-31`
+
+**Operator:** [Anish Raj](mailto:raj@cubert-gmbh.de) — Cubert GmbH
+
+## Hardware
+
+- **Camera:** Cubert Ultris XMR (serial 254902)
+- **Lens:** 50 mm / f2.0
+- **Accessories:** None
+
+## Setup & Lighting
+
+- **Light source:** Halogen (4 lights in 4 configurations)
+- **Working distance:** 46.6 cm (466 mm)
+- **Field of view:** ≈12.5 × 12 cm
+- **Notes:** Four lighting configurations used per arrangement:
+  - `l0` — all four lights on
+  - `l1` — front and back lights only
+  - `l2` — front and two side lights
+  - `l3` — front light only
+
+  All four frames of the same scene arrangement form a `group_id` in `splits.csv`
+  and are always kept in the same train / val / test split.
+
+## Acquisition Settings
+
+- **Measurement mode:** Snapshot (single capture per lighting config)
+- **Integration time:** 15 ms
+- **White reference:** 55 % gray target
+- **Dark current:** Recorded
+- **Processing mode at rest:** `Preview` — call `cuvis.ProcessingContext(sf).processing_mode = cuvis.ProcessingMode.Reflectance; ctx.apply(m)` before reading `m.cube`
+
+## Frames in this `.cu3s`
+
+| | |
+|---|---:|
+| Total saved frames | **17** |
+| Frames with foreign-object annotations | **0** |
+| Train / val / test split | **10 / 3 / 4** |
+| `global_frame_id` range (day) | `2 .. 18` |
+| `local_image_id` range (this cu3s) | `0 .. 16` |
+
+## Annotations
+
+| Class | Frame-level count |
+|---|---:|
+
+
+Annotations are semantic-mask COCO polygons. See [`2026_03_03_11-31-31.json`](./2026_03_03_11-31-31.json).
+
+## Scene description
+
+Mixed beluga + dark green marbled lentils (Emershofer brand) arranged on the
+conveyor-belt material. Foreign objects placed by hand into the bulk product.
+For each arrangement, four snapshots are captured (one per lighting config) to
+study how illumination affects spectral separability.
+
+## Credits
+
+Recorded and processed by the AI Team @ Cubert. See the top-level
+[`README.md`](../../README.md) for the full dataset description, load snippets,
+example frames, and split methodology.