1977 - C-FORMAT - Ampex / Sony (IEC 558)
This non-segmented format reflects the third iteration of the SMPTE 25.4 mm helical video recorder standard. Appearing in 1978 this format was designed to provide 'stunt' capabilities such as still-frame, picture-in-shuttle and slow motion that were impossible with 'quad' recorders. C-format was the vehicle for the introduction of AST (auto scan tracking) and the PAL variant was promptly embraced by the EBU.
| Signal system | ||
| Analogue, composite, non-segmented. | ||
| Scanner | ||
| Geometry | Helical | |
| No. of rotating heads | 3 or 6 * | |
| Scanner diameter (top) | 134.62 | mm |
| Rotation speed | 50 | rev/s |
| Tracks/revolution | 1 | |
| Head-to-tape speed | 21.39 | m/s |
| Video track angle | 2.56 | degree |
| Track width | 160 | µm |
| Track pitch | 214 | µm |
| Azimuth | Perpendicular | |
| Tape Properties | ||
| Coercivity | 650 | Oe |
| Type | Cobalt-modified oxide | |
| Width | 25.4 | mm |
| Thickness (total) | 28 | µm |
| Tape Consumption | ||
| Linear | 239.8 | mm/s |
| Areal | 0.37 | m2/min |
| Shelf volume | 952 | cm3/h |
| Electrical Characteristics | ||
| Sync tip carrier frequ. | 7.16 | MHz |
| Blanking | 7.68 | MHz |
| Peak white | 8.90 | MHz |
| Shortest wavelength | 2.4 | µm |
* Normal configuration with 3 heads has vertical interval 'dropout' and space for four longitudinal audio tracks. 6 heads option provides continuous recording with space for 3 audio tracks. One variant uses the 'sync' track space for digital audio. IEC 558
