User Guide

overshoot. However, at small sizes this overshoot should
drop out and the letters should be the same height. The
oversize is typically 4%, which means that if 4% of the em
square is less than one pixel, there should be no overshoot.
The way overshoot is controlled in a Type 1 font is through
a blue zone. Only Adobe knows how they derived that
term, but the concept is to specify important vertical
alignment coordinates in a table.
Blue zones are not associated with particular characters,
they apply to the entire font. However, it is helpful to think
of them as corresponding to certain groups of characters.
When Fontographer computes or recomputes the vertical
alignment zones, the first pair of values is based on
characters such as “A” and “C,” which are normally
drawn with their bottoms on or near the baseline. The first
value of the pair is the baseline overshoot (characters such
as “C” and “O”). The second value is the normal baseline.
The remaining blue zones are computed from the tops of
characters and the x-height (characters such as “c”
and “x”); the cap height line (“H” and “O”), and the
ascender line (“d” and “l”). Since the zones cannot overlap,
the ascender zone may not be found. The Other blues are
based on the bottoms of characters such as the descender
line in characters “g” and “y.”
Choosing “Vertical Alignment Zones” from the Hints menu
brings up this dialog.
These fields are named after Bob Dylan’s famous hinting-
inspired ballad, “Tangled up in Blues.” Well, maybe
not—we don’t really know why these fields are
called “Blue values” and “Other blues.” Of course, we
know why they are in this dialog—we typed them in that
way! What we don’t know is why the PostScript hinting
variables these were named after have anything to do with
the color blue. But they do, and once again, you are
encouraged to look at Adobe’s Type One Font
Specification, which covers the ins and outs of PostScript
Fontographer User's Manual
10: Expert Advice Page #24