The parameters [min/max]FaceSize for each IDKit API function designated for face detection allow us to define the face size.

The face size is defined as a maximum of inner pupil distance and distance between the center of the mount, and a center point between eyes.

If you want to specify the face size relative to the maximum of the input image, just set the values of range <0, 1>.

If the values are higher than 1.0, they represent the absolute distance in pixels.