When generating GN4 font metric from AFM Type I font files

If the GN4 font metric is generated from AFM Type I font files, the GN4 applet that generates the font metric does not have to calculate - all the values are just read from the AFM font file. The font PostScript names will always be right ones and the kerning tables will be complete. The precision of typographical correspondence for character widths and positions is the highest possible. However, the screen font names will need a manual adjustment.

When generating GN4 font metric from TTF or OTF font files

If the GN4 font metric is generated from True Type or Open Type font files, GN applet that generates the font metric has to calculate all the typographical values, reading data from the True Type or Open Type font itself. The PostScript names of fonts will sometime be wrong, therefore, you will have to replace them with correct names. The kerning tables sometimes may be incomplete or absent. The precision of typographical correspondence for character widths and positions is lower, because of rounding during calculations.