PC-IV · 1931
Archive Plate Camera
Records to glass because glass does not move.
Silver halide on a ground glass substrate, held flat to two microns across the full field. Film breathes with humidity and gelatin creeps over decades. Glass does neither, which is why the 1931 plates in our archive still measure true against the originals.
Specifications
| Plate format | 240 × 240 mm |
|---|---|
| Flatness | 2 μm across field |
| Emulsion | Fine-grain orthochromatic |
| Exposure range | 1/60 s to 14 hr |
| Focal length | 1 220 mm |
| Mass | 94 kg |
Applications
- 01Astrometric survey
- 02Long-baseline reference
- 03Permanent record keeping