Republic, and several companies buy bulk quantities of 16 mm film to make regular 8 mm by re-perforating the stock, cutting it into 25 foot (7.6 m) lengths, and collecting it into special standard 8 mm spools, which they then sell. Re-perforation requires special equipment. Some specialists also produce Super 8 mm film from existing 16 mm or even 35 mm film stock. Sound When Eastman Kodak first conceived the 8 mm format, no provision was made for the addition of a sound track. Nevertheless, in the 1960s, projectors appeared on the market that were capable of recording and replaying sound from a magnetic stripe applied to the film after it had been processed. The only part of the film wide enough to accept such a magnetic stripe was the area between the edge and the perforations. A much narrower stripe was sometimes added to the opposite edge so that the film piled up evenly on the spool, but was never used for sound. The sound to picture separation was the same dimensionally as 16 mm film, and as that format is 28 frames, that meant that the Double-8 system was 56 frames. The proximity of the sound stripe to the perforations caused some problems in keeping the film in close contact with the sound head. There was never an optical system. A few sound prints appeared for use in Double 8 projectors. Super 8 In 1965, Super-8 film was released and was quickly adopted by many amateur film-makers. It featured a better quality image and was easier to use mainly due to a cartridge-loading system that did not require reloading and rethreading halfway through. To easily differentiate Super 8 film from Standard 8, projector spools for the former had larger spindle holes. Therefore, it was not possible to mount a Super 8 spool on a Standard 8 projector, and vice versa. Sound The Super 8 format was designed from the start to accommodate a sound track (one of the few film formats to do so). This track would occupy the area between the edge of the film and the image area. As in the double 8 system, a second stripe was sometimes added between the edge and the perforations. The image to sound distance was much shorter for the Super 8 system at just 18 frames. At first, the magnetic stripe had to be applied after the film was