/diy/ - Do It Yourself

I'm trying to figure out the intensity (mW/mm^2) of light emitted on a small section of a plane above an LED. The square is small enough that I'm assuming the intensity is constant and depends only on phi. I know that I(Phi) = dFlux/dPhi. But I'm having a hard time figuring out where to go from there. My current best guess is that the relative luminous intensity chart is showing the intensity relative to 2.5mW/sr. If that's the case, then at Phi, adding some dPhi adds a certain flux which I can find from the chart, and I also can find the amount of surface area of a partial sphere that's added when I add that dPhi, then dividing dFlux/dArea will give intensity... does that sound correct? Is there some shortcut I can take since the total emitted power is given?