User Guide

(found in the Font Info dialog) are measured in em units,
as are all measurements in Fontographer. The sum of
these two values defines the em square.
Units
Fontographer units are values whose size is relative,
varying with the size of the em-square and the point size of
the output. Because outline fonts are scaleable, units do
not directly relate to points, pixels, or any physical distance.
It is possible to relate units to physical distance if the em-
square is set up knowing the printing device resolution and
scale at which the font is to be printed, but this defeats
the whole concept of outline fonts. We recommend that
you forget about trying to relate units to distance and think
of them as design units whose dimension may vary.
Fontographer is capable of defining fonts with an em
square of up to 8,000 by 8,000 units. This range is far
greater than needed for any normal font. Most PostScript
fonts have an em square of 1000 units, which is also
Fontographer’s default. Precise work for high-resolution
printers above 1000 dpi might benefit from an em square
of 2,000 or more. The choice of em square size is left up
to you.
Choosing a larger em square means that you have more
precision when outputting the character. It does not mean
that the printed characters are larger. Since a font is
always normalized so that the em square is one point high,
a font defined with an em square of 4,000 prints out at
exactly the same size as a font defined with an em square
of 1,000. It has four times the internal resolution, but that is
insignificant on a 300 dot per inch printer except at very
large point sizes. A 1,000-point high character (almost 14
inches) would have at most 1/72 inch of inaccuracy if
drawn on a 1,000-unit em square. If drawn with a 4,000-
unit em square, the inaccuracy would be approximately
one dot (1/288 of an inch). Proper positioning of the
control points, whatever em square size is used, is more
important than greater resolution.
Unique PostScript ID
This ID is used for caching character images in your
printer, thereby decreasing printing time. Font IDs for new
Fontographer User's Manual
C: General information Page #4