Back in the days of 35mm film, a 50mm prime was considered a 'standard' lens. That's because it gives pretty much the same perspective as viewing a scene with the human eye, without the magnification of a telephoto lens or the shrinkage a wide-angle lens uses to squeeze more into the frame.
The flexi disc (also known as a phonosheet or Soundsheet, a trademark) is a phonograph record made of a thin, flexible vinyl sheet with a molded-in spiral stylus groove, and is designed to be playable on a normal phonograph turntable.
Fig 1: Healthy Microtome Section. (larger view). The vertebral disc in the spine is an interesting and unique structure. Its primary purpose is to act as a shock absorber between adjacent vertebrae.Spinal discs also act as ligaments that hold the vertebrae of the spine together and as cartilaginous joints that allow for slight mobility in the spine.There are a total of twenty-three vertebral discs in the spinal column.Specific problems with any of these discs may prompt different symptoms, including back pain, neck pain, and sciatica. 1  See All About Spinal Disc Problems.here are a total of twenty-three vertebral discs in the spinal column. Specific problems with any of these discs may prompt different symptoms, including back pain, neck pain, and sciatica. 1  See All About Spinal Disc Problems.