ptgrey camera sensor size (pixel - mm)

If it is necessary to extract the focal length of the camera from the (calibrated) camera matrix, one needs to know the physical dimensions of the CCD (the number of pixels in both x- and y directions are easy to find, but not the physical dimensions). The information about the CCD size that is is commonly given for your camera is quite a mystery. I am using ptgrey with 1/1.8'' CCD size. A brief but informative explanation is given by http://www.dpreview.com/learn/?/key=Sensor_Sizes
-- some comments from cu