A microscope c-mount adapter is what mates a microscope camera to the microscopes trinocular port. The camera threads onto the top of the c-mount and the c-mount is attached and secured to the microscope. In a perfect world the c-mount should be the same brand as your microscope, this will ensure parfocality. Usually a microscope c-mount adapter will have reduction lenses inside in order to better match the the image on the computer or screen to the field of view of the eyepieces. C-mounts are marked with the reduction magnification for example, .3x, .45x, or .7x.
How to Buy Microscopes: Which C-mount do I need?
In order to determine the magnification of the c-mount you need you will first need to know the specifications of the camera you intend on using. The information you will need is the camera chip size or sensor size. Some examples of camera chip sizes are - 1/4", 1/3", and 1/2"
In order to determine which c-mount you need you will divide the first number in the chip size by the second number in the ship size.
For Example: Chip Size 1/2"
This means you will want to use a .5x microscope c-mount adapter.
What happens if you do not get an even number?
For Example: Chip Size 1/3"
You will want to round up or down to the closest c-mount available. For this instance you will choose a .3x c-mount.