function B1 = B1calc (p, AF)
%B1calc(p, AF)	Calculates B1, an essential constant in determining how 
% 	the pointspread function is effected by pupil size. Input variables 
%	are as follows:
% 
%p = pupil size in mm
%AF = age factor (calculated with agefact)
%
%Output value is in c/rad^-1
d = 3.2;
B1 = (1 + (p/d)^2 )/(bcalc(AF)*p);