BFD-P file consists those ellipses in which the perception is equal to inside the center of ellipses
 and outside of the ellipses the perception is preceived difference.
there are eighty ellipses.

BFD-A file is  for acceptance threshold ellipses. inside of the ellipses acceptances is equal to the center and outside is different. 
There are altogether 50 ellipses.

BFD(2) file is a merged file of above two . The first eighty ellipses are type P and the rest are type A.

x(0) y(0)            YL          A          RRR            TT

Chrom center      Luminance	a/1000	   e=a/b	 angle
CIE 64					   b=a/RRR