Fit C-Mount Lenses on CS-Mount CCTV Cameras with a 5mm Adapter Ring The 5mm C-CS Mount Lens Adapter Ring CCTV solves a small problem that wastes a lot of time on site: your lens and your camera use different mounts. C-mount and CS-mount lenses use the same thread, but a CS-mount camera places the sensor 5mm closer to the lens seat than a C-mount camera does. Thread a C-mount lens straight onto a CS-mount body and the image never reaches sharp focus. This ring adds the missing 5mm, so you keep your existing lens and finish the job in one visit. It is a plain mechanical spacer, so you need no software, no drivers, and no setup.How the 5mm Spacing Works at the Mount The standard flange focal distance for C-mount is 17.526mm, and CS-mount uses 12.526mm. That 5mm gap is exactly what this ring fills. You screw the ring onto the CS-mount camera, then thread the C-mount lens onto the ring. The lens now sits at the correct distance from the sensor, so your focus ring and zoom ring work the way the lens maker intended. Without the ring, you turn the focus ring to its end stop and the picture stays soft. The ring changes nothing in the lens optics or electronics apart from the added spacing, so your image quality depends on your lens and camera, not on the adapter.Where You Use It in Your Day-to-Day Work Reach for this ring whenever the mount on the lens and the mount on the camera do not match. A common case: a shop owner already has a C-mount varifocal lens from an old camera, and the new camera has a CS mount. Instead of buying a second lens, you fit this ring and hand the system back working. CCTV technicians also use it during camera replacement and system maintenance, when the new body uses a different mount than the old one. Industrial and surveillance cameras with C/CS mounts accept the ring the same way. You can also fit it between a C-mount lens and a C-mount camera as a short extension tube for closer focusing, but that changes your focus distance, so use it only when you want that effect.Fitting Tips and Related Tools Clean the threads on the lens and the camera before you fit the ring, because dust on the thread ends up near the sensor opening. Hand-tighten the ring and the lens without force. If a thread binds, back the lens out and start again, because a cross-threaded mount damages both parts. Check your camera’s mount type first: a CS-mount camera with a C-mount lens needs this ring, but a C-mount camera with a C-mount lens needs none. Do not use this ring to mount a CS-mount lens on a C-mount camera, because that setup already sits too far from the sensor and the ring makes it worse. If you build a camera setup for your repair bench, browse our Microscopes category and match each camera’s mount type before you order. For wider CCTV jobs, keep a few adapter rings in stock, so you never lose a half day waiting for one small part.
