High dpi using print function

if true
  % fig = gcf;
% fig.Color = 'w'; %background color.
% fig.DockControls = 'off';
% fig.RendererMode = 'manual';
% fig.Renderer = 'painters';
fig.Units = 'centimeters';
% fig.Resize = 'off';
% fig.InvertHardcopy = 'on';
fig.PaperPositionMode = 'manual';
fig.PaperUnits = 'centimeters';
% %Con l'orientazione landscape inverte width e height.
fig.PaperOrientation = 'portrait';
fig.PaperSize = [84.1 59.4];
fig.PaperPosition = [4.205 2.97 75.69 53.46];
directory = 'C:\Users\Amministratore\Desktop\Imm5';
print(directory, '-painters', '-dtiffn', '-r900');
end

I'm using this code to save an high resolution image. This works fine. But when I increase -r900, for example using -r1200, the image turns out black. Is there a resolution limit? What is it? I'm working with MATLAB 2015a.