C-Mounts, CS Mounts and Image Sensors

A c-mount adapter for your microscope without a lens in it, is merely a connector for your camera. What you'll get is a "direct image" on the monitor screen, which is more magnification than what is seen in the eyepieces due to the inherent magnification with image sensors and microscopes. While this arrangement is fine for some users, others require an image on the monitor that looks more like the Field Of View, or FOV, that is seen in the microscope eyetubes.

To compensate for too much mag or to match more closely the microscope FOV, one can use c-mounts with reduction lenses in order to adjust the field of view seen on the monitor. The reduction lens you require will depend on the chip size of your camera so if your camera has a 1/2" image sensor, you'll want the 0.45X c-mount. See the table at right for other adapter suggestions. Experienced users have an assortment of reduction lenses to accommodate different situations or specimens as c-mounts are relatively inexpensive.

Camera Chip SizeSuggested Adapter
1/4" 0.265 or 0.3X
1/3" 0.3X
1/2" 0.45X, 0.5X or 0.6X
1/1.8" 0.45X, 0.5X or 0.6X
2/3" 0.7X

Difference between “C” mount vs “CS” mount explained

C- and CS-mount lenses are both threaded lens mounts found on most industrial CCD cameras and lenses. The difference between C and CS-mount equipment is the distance between the flange of the lens (the part of the case that butts up against the camera) and the focal plane of the lens (where the CCD sensor must be positioned). This is known as the flange back distance.


The C-mount lens specification for flange back distance is 17.53 mm, and on CS-mount lenses it is 12.53 mm. However, on Point Grey cameras, these physical distances are offset due to the presence of both a 1 mm infrared cutoff (IRC) filter and a 0.5 mm sensor package window. These two pieces of glass fit between the lens and the sensor image plane. The IRC filter is installed by Point Grey on color cameras; in monochrome cameras, the IRC is replaced with a transparent glass window. The sensor package window is installed by the sensor manufacturer. The refraction of these glass components requires an offset in the flange back distance from the nominal values.


If you have a CS-mount camera and a C-mount lens, you can add a 5mm spacer to obtain the correct focus. If, however, you have a C-mount camera and a CS-mount lens, correct focus cannot be achieved.


As one can see, image sensors in cameras are actually quite small. The smaller the sensor, the more inherent magnification. The larger the sensor, the better the resolution with less magnification.

As image resolution is most desirable in all microscopy applications, 1/4" chips are just not well suited for microscopy while the 1/2" and 2/3" chip cameras strike a better balance between magnification, resolution and the size of the virtual image that the camera is seeing which to the eye appears much like a flashlight beam.


Meiji Techno C-Mount Adapters with reductions lenses are easily removed from the optical path by simply removing the black colored lens piece and then re-attaching the camera to the tube directly when higher on-screen magnification is needed. Click HERE to try our On-Screen Magnification Calculator Page to see how different combinations of objectives, auxiliary lenses, c-mounts, camera chip sizes and monitor sizes effect the magnification seen on the monitor screen.

C-Mounts and CS-Mounts

CCD or CMOS Cameras with the one-inch threaded aperture are an industry standard.

Meiji Techno cameras have "CS" mounts so they can also accommodate "C" mounts when a spacer is first threaded onto the camera providing the additional 5mm per the "C"-Mount specification as shown above.

The V-5MM is included with all the CK Series Analog Video Cameras that Meiji sells and supports. The adverse result that can happen when a spacer is not installed is a phenomenon known as "vignetting".

For those wanting to use Meiji C-Mounts on their old microscope, here are the dimensions you'll need to know:


Sensor Size Designations Explained

Sensor sizes are often designated using fractions such as 1/1.8" or 2/3" which are larger or smaller than the actual sensor diagonal dimension. This sensor size designation goes all the way back to standard sizes given to Vidicon camera tubes developed in the 1940's and is unfortunately, still in use today.

Common Image Sensor Sizes
Sensor "Size"Aspect RatioActual Sensor Dimensions (mm)
1/4" 4:3 4.000 3.200 2.400
1/3.6" 4:3 5.000 4.000 3.000
1/3.2" 4:3 5.680 4.536 3.416
1/3" 4:3 6.000 4.800 3.600
1/2.7" 4:3 6.721 5.371 4.035
1/2.5" 4:3 7.182 5.760 4.290
1/2" 4:3 8.000 6.400 4.800
1/1.8" 4:3 8.933 7.176 5.319
1/1.7" 4:3 9.500 7.600 5.700
2/3" 4:3 11.000 8.800 6.600
1" 4:3 16.000 12.800 9.600
4/3" 4:3 22.500 18.000 13.500
1.8" (APS-C) 3:2 28.400 23.700 15.700
35 mm film 3:2 43.300 36.000 24.000

Below is a list of popular digital cameras and their sensor size.

This list is for information only and does not constitute an endorsement of any kind.

CameraSensor TypePixel countSensor size
Minolta DiMAGE Xg 1/2.7" CCD 3.3 million 5.3 x 4.0 mm
Canon PowerShot S500 1/1.8" CCD 5.0 million 5.3 x 4.0 mm
Olympus C-8080WZ 2/3" CCD 8.0 million 8.8 x 6.6 mm
Sony DSC-828 2/3" CCD 8.0 million 8.8 x 6.6 mm
Minolta DiMAGE A2 2/3" CCD 8.0 million 8.8 x 6.6 mm
Nikon D70S 1.8" CCD 6.1 million 23.7 x 15.7 mm
Nikon D2X 1.8" CMOS 12.2 million 23.7 x 15.7 mm
Kodak DSC-14N CMOS 13.8 million 36 x 24 mm
Nikon D2X CMOS 16.6 million 36 x 24 mm


As new cameras come into the market each month, it is a never ending task to stay informed. Meiji Techno Co., Ltd. is committed to developing quality camera adapters for the most viable makes, models and form factors.