The documentation cuts off mid-sentence on both the 2.4 and 3.0 version sites... (link: http://docs.opencv.org/3.0-last-rst/modules/face/doc/facerec_api.html#createlbphfacerecognizer)
radius – The radius used for building the Circular Local Binary Pattern. The greater the radius, the
My guess at this from reading a paper on LBPH is that the radius is related to the area considered for each patch?
I'm trying to figure out a good value for this and it would be nice to know exactly what the different values correspond to.
From a similar thread in OpenCV:
A small radius of the operator makes the information encoded in the histogram more local. THE GREATER THE RADIUS, the smoother the image but more spatial information you can get.
You might find also useful this repository:
Now using an abritrary radius and sample points has two effects. The more sampling points you take, the more patterns you can encode, the more patterns (and probably information) you have, but the higher the computational effort. Instead the larger the radius, the smoother the LBP image, the larger details can be captured, the less discriminative power the description may have (if you don't increase the sampling points at the same time).