The capture device is responsible to take images. The images are used in the four pass way.
Kerberos supports a whole range of USB cameras. You will find a complete list here. Make sure that you've updated the settings page on the web interface, that you will be using an USB camera.
Kerberos can be used with any IP camera, that provides a streaming URL. Make sure that you know the correct URL of your IP camera, you can find a list here. Make sure you have updated the web interface, to make Kerberos aware you will be using an IP camera.
Raspberry Pi camera
You can use the Raspberry Pi camera (v1.3 and v2.1) with Kerberos.io, you just need to attach the camera and you are ready to go. The Raspberry Pi Camera Module is enabled by default in the web interface. Please note that if you are running Raspbian, you'll need to enable the camera module yourself.
Using the Raspberry Pi camera will give the best performance, because Kerberos.io uses hardware acceleration for both the live streaming and the video recording. On a Raspberry Pi Zero W, HD/30 FPS can be achieved with ease.