[ft] sub pixel rendering does not work

[newltf]

I enable cleartype by uncomment macro FT_CONFIG_OPTION_SUBPIXEL_RENDERING and
write follow :

FT_Load_Glyph(Face, glyph.FtIndex, FT_LOAD_TARGET_LCD);
FT_Render_Glyph(Face->glyph, FT_RENDER_MODE_LCD);

the font become very large that is descriped by the comment “For example,
using FT_RENDER_MODE_LCD when calling */
  /* FT_Render_Glyph still generates a bitmap that is 3 times wider than   */
  /* the original size in case this macro isn't defined;”

what is the problem?