processed and recorded on a suitable projector. In the 1970s, cameras appeared which were able to record live sound directly onto pre-striped film. This film was loaded into oversize cartridges that provided access for the camera's sound recording head. The camera would also accept non sound cartridges, but silent cameras could not accept sound cartridges. One major advantage of the Super 8 system was that as the camera pressure plate was a part of the cartridge, it could be moulded to the profile of the stripe(s) on the film. Projectors also appeared on the market which took advantage of the balance stripe next to the perforations by recording and replaying stereo sound. Projectors appeared in the late 1970s that featured the ability to play films with an optical soundtrack. The image-sound separation for the optical format was 22 frames. These were never popular in the English speaking world and are consequently very rare in those countries, but they did enjoy some popularity in the Far East and Europe mainly because optical prints were cheaper. Sound prints in Super 8 were plentiful and considering that they were very expensive by modern-day standards, sold in appreciable quantities. A two-reel print (running approximately 17 minutes) cost around $50 with feature films costing at least $150-plus. A few prints were also released with stereo sound. In Europe, optical prints were also popular and were appreciated for their often superior sound quality. In theory, magnetic prints should have been superior, but Super 8 magnetic prints were often poorly recorded after the picture was processed, due to high-speed, mass production techniques. An optical track, on the other hand, could be printed at the same time as the image and in equivalent quality. Single 8 Another version of Super 8 film, Single-8, was produced by Fuji in Japan. Introduced in 1965 as an alternative to the Kodak Super 8 format, it had the same final film dimensions but with a different cassette. Unlike the co-axial design of Super 8, the Single 8 cartridge featured one spool above the other. Sound Single 8's film format being identical to Super 8 means that everything written above regarding projectors for Super 8 applies equally to Single 8. Cameras also appeared for the Single 8 system that were capable of directly recording to pre-striped film which was presented in an oversize Single-8 cartridge which provided access for the camera's sound recording