function Mb = Mbcalc(i, q, AF, p, m)
%Mbcalc(i, q, p, AF, m) Calculates Mb, an intermediate in the calculation of
%	the Modulation transfer function. Modeling based on Ijspeert, 1992.
%	However, this function can be used independently of the MTFip function.
%
%SEE: MTFip
switch nargin
	case{1}
		error 'too few arguments' 
	case{2}
		age = 0;
		p = 4;
		m = pigment;	
	case{3}
		p = 4;
		m = pigment;
	case{4}
		m = pigment;
	case{5}
	case{nargin>=6}
		error 'too many arguments'
end

switch i
	case{1}
		Mb = exp(-360 * B1calc(p, AF) * q);
	case{2}
		Mb = exp(-360 * B2calc(p, AF) * q);
	case{3}
		Mb = exp(-360 * B3calc(AF, m) * q);
	case{4} 
		Mb = exp(-360  * q);  % B4 = 1 by definition
end