Originally, most 70 mm films were filmed on 65 mm negatives. Filming in 65 mm ended (with few exceptions) in the 1960s, but through the 1990s many movies were filmed in 35 mm and "blown up" to 70 mm for release. A number of theaters had 70 mm projectors and, from a marketing point of view, 70 mm had a certain cachet. But there were real advantages, as well. Until the advent of digital soundtracks in the 1990s, the 70 mm 6-track magnetic sound was far better than 35 mm optical stereo. 70 mm projectors typically also had better brightness, image stability and definition.