A microscope c-mount adapter allows you to connect a microscope camera to the trinocular port of your microscope. C-Mount adapters are microscope-specific, which means that if you are using a Meiji microscope, you need the Meiji c-mount adapter to connect your camera. Image at left is a Motic C-Mount adapter for the SMZ stereo microscope.C-Mount adapters have a standard 1" (25mm) diameter thread. The c-mount adapter allows you to connect any brand of microscope camera with c-mount threads, to your microscope. The c-mount adapter has a reduction lens in it. This allows the camera to see a similar magnified image compared to what the eyepieces see. Depending on the size of the chip in your camera (1/2", 2/3", etc.), you would want to choose a different magnification c-mount adapter. When using 10x eyepieces and a camera with a 1/2" chip in it, you would want to select either a 0.45x or 0.5x c-mount adapter. You can learn more about how to select the correct magnification c-mount adapter here.
Meiji C-Mount adapters varying from 2.5x - 0.3x.