Saveas to .jpg not same size as .fig

Hi

I use saveas to save the figure in both .fig and .jpg formats. However, when I open the jpg it appears that it has not adopted the resolution I set which works for the .fig.

I thought this was something to do with 'PaperPosition' property value after seeing this answer, although I can't get this to work? http://www.mathworks.com/matlabcentral/newsreader/view_thread/245012

plot(abc)
figSize = [1 1 800 500];  % the desired resolution and figure size
set(gcf, 'Position', figSize); 
set(gcf, 'PaperPosition', figSize);
saveas(gcf,abc.fig);
saveas(gcf,abc.jpg);

[Walter Roberson]

I do not understand. You cannot set a resolution for a .fig . A .fig file effectively has vector graphics primitives -- the handle graphics, not the rendered figure.