function MTF = MTFip(q, p, age, m)
% MTF = MTFip(q, p, age, m) Calculates the modulation transfer function (MTF)
%	based on data from Ijspeert et al. 1992. All input variables are optional
%	except for q
%
%Input variables:
%	q = frequency in c/deg		
%	p = pupil diameter in mm		Default = 4 mm
%   age = age in years				Default = 0 years
%	m = pigmentation parameter		Default = call to pigment function
%
%SEE rad2deg, deg2rad
switch nargin
	case{nargin<1}
		error 'too few arguments'
	case{1}
		age = 0;
		p = 4;
		m = pigment;	
	case{2}
		age = 0;
		m = pigment;
	case{3}
		m = pigment;
	case{4}
	
	case{nargin>=5}
		error 'too many arguments'
end

AF = agefact(age);

for i = 1:4
	switch i
		case{1}
			c1 = c1calc(AF, p, m); 
			Mb1 = Mbcalc(i, q, AF, p, m); 
		case{2}
			c2 = c2calc(AF, p, m);
			Mb2 = Mbcalc(i,	q, AF, p, m);
		case{3}
			c3 = c3calc(AF, m);
			Mb3 = Mbcalc(i, q, AF, p, m);
		case{4}
			c4 = c4calc(AF, m);
			Mb4 = Mbcalc(i, q, AF, p, m); 
	end
end
%Normalization of c prefactors to 1
ctotal = (c1 + c2 + c3 + c4);

MTF1 = (c1/ctotal) * Mb1;
MTF2 = (c2/ctotal) * Mb2;
MTF3 = (c3/ctotal) * Mb3;
MTF4 = (c4/ctotal) * Mb4;

%Final Summation
MTF = MTF1 + MTF2 + MTF3 + MTF4;