Why can't I render text identical (pixel-perfect) as Ubuntu 11 using FreeType2.4.4?

I've been working on this for days.

I'm trying to render a character (with subpixel hint开发者_开发技巧ing) that exactly resemble the Ubuntu's LCD slight mode. I've already set FT_LOAD_FORCE_AUTOHINT | FT_LOAD_TARGET_LIGHT as load flags.

Below shows the contrast, both Georgia, 12px, #fff. As you can see, on Firefox colors are milder and there is an extra column on either side. By the way, gnome-terminal's rendering is identical to Firefox's.

There are 4 levels of hinting in Ubuntu — None/Sligh/Medium/Full. How do I render my text in these levels? I know Ubuntu uses Pango for text rendering and Pango in turn uses Freetype to rasterize glyphs, so I think using Freetype, it is possible to exactly resemble what Ubuntu does.