Apple Aperture has a function "Show Focus Points". When I am using it with raw files from Canon 500D, it displays the pattern of focus points (just like the camera viewfinder) and highlights some of them.
First I thought that it would do the obvious thing: it would just show which focus points were active (either the focus point that was selected manually, or the focus points that the camera selected automatically).
However, the results did not seem to match the reality; there were some red rectangles, but they seemed to be in the wrong places. And then I had a bit closer look at the display and realised that there are (at least) four different kinds of rectangles:
- thin white
- thick white
- thin red
- thick red
What do these different symbols mean? Not all of them are visible in all photos, but I was able to find photos that actually had all four types of rectangles.
I would guess that one of the following explanations is close to the reality:
- thick rectangles (both white and red) show the focus points
- thick white rectangles show the focus points.
But what do the colours mean, then?
Edit: Here is a quick test shot that shows what I see. I had set the camera to automatically select the AF points. According to the flashing lights in the viewfinder, the camera selected the center point (= thick red) and the lower right point (= thick white). But then why is the rightmost AF point shown as a red box?