function whatever(a,b)

if nargin==0
  a=1.65;b=-12.5;
end%if

%load  -force  ../comparunroll/Jsum03.cls_fast.mat  % matlab doesn't understand
load  ../comparunroll/Jsum03.cls_fast.txt
%Finv=lnFinv;
Finv=Jsum03;

load ground_truth_d1_response_function_data_consolidated.txt
Q=ground_truth_d1_response_functi(:,1);
f=ground_truth_d1_response_functi(:,2);

% sort in case we want to plot with line instead of points:
[Qsort, ind]=sort(Q);
Q=Qsort;
f=f(ind);

q=(cbrt(2)).^Q;

plot(Q,f,'+');
axis([min(Q),max(Q),0,255])
xlabel('Q (Quantity of light)','FontSize',20) % Q=log_cbrt{2}(q)
ylabel('f (response byte)','FontSize',20)
title('estimated camera response function with ground truth data','FontSize',14)
grid

hold on
plot(a*Finv+b,0:255); % affine fit (arbitrary unknown constants, move to fit)
hold off

