In most builds you want to go with an m12 lens setup, though the CS lenses do allow more light to hit the sensor and are typically made of higher quality glass optics. The mm number of the lens relates to the focus distance and thus the field of view (FOV) of the lens. The smaller the mm number, the larger the FOV (the larger mm the more FOV). The more FOV you have the more barrel/curved distortion you will have in your image. More distortion means the light passing through the band pass filter will be shifted outside the very narrow nm band of light being allowed to pass through to the camera sensor. This means less bright blobs at the edges of your touch screen and makes calibration in the tracking program (CCV) more difficult (if not impossible in very distorted setups). Thus, you want to always minimize the distortion so that you get the most light to the sensor, and bright even blobs over the entire surface.

For finger tracking setups it is best not to use a lens of less than 2.8mm.
For fiducial tracking setups, it is best not to use a lens less than 3.6mm.

If you need to use a lens below the mm listed above, it is recommended that you either use multiple cameras, or a lens which has internal distortion correction, like some of our CS lenses. If you do use a lens of less mm (not recommended), you will need to either compensate for the distortion light shift with more lights and distortion software correction.

You can find more m12 and CS lenses also on our store