The Difference between C Mount and CS Mount Lens

  The flange back is the distance from the surface to the focal point. The flange back of CS-Mount lens is 12.5mm which is 5mm shorter compared to C-Mount lens. This is the only difference between the C-Mount lens and CS-Mount len. You’ll need a 5mm spacer ring when you mount a C-Mount lens to some CS-Mount camera. CS-Mount camera is always suitable for C- or CS-Mount lens. But, C-Mount camera isn't suitable for CS-Mount lens. Most professional cameras are CS-Mount cameras including a C-ring. A 5mm spacer ring is necessary when a C-Mount lens is mounted to a CS-Mount camera unless the camera has built-in Flange-back Adjusting Ring.