MetaFont
Standard Transformations on Fonts

The MetaFont dialog (obviously the name is a rip-off of Knuth's work) will try to find important features of a font and a character and allow you to modify them. It does not read TeX .mf files. The features searched for are:

The results will probably always need to be examined and fixed up by the human eye, but they may provide a help in changing a font's attributes. At the moment the command is pretty primitive.

It "works" best on sans serif, non-Oblique fonts.


Bold

Bold fonts have thicker stems and are slightly more extended than normal fonts. In Knuth's Computers & Typesetting, the bold fonts have a stem width that is approximately 1.6 (1.68(at 12pt)-1.5(at 5pt)) times the stem width of the normal font. This is very similar to the 1.75 suggested by Microsoft's ratio of 700/400 (700 being the numeric weight of a bold font, and 400 being the numeric weight of a normal font).

In Knuth's Computer Modern Bold Extended Roman, the "m" character is extended to 1.15 times the width of the "m" in Computer Modern Roman, and the x-height is 1.03 times higher.

Font Ratio of Bold/Regular Stems Ratio of DemiBold/Regular Expansion Bold serif height/Regular serif Bold serif width/regular
Arial 1.5 1
Times New Roman 1.7 1 .98
Computer Modern Roman 1.68(at 12pt) - 1.5(at 5pt) 1.15
Adobe Helvetica 1.6
Adobe Times 1.56 1.17 1.10 .97
Garamond Antiqua 1.5 1.05 .90

Point Size

At first glance this does not seem like much of a transformation, after all postscript and truetype fonts can be drawn at any pointsize. But traditionally, as the point-size decreases the boldness (thickness of the stems) increases slightly, the counters and side bearings also change. For metal type there were generally three drawings for a character in a given font, one for pointsizes less than 10, one for pointsizes 10,11 and 12, and one for display sizes (above 12). Most computer vector fonts do not show this change, while Knuth's Computer Modern fonts have a continuum:
Stem width, scaled by point size, made relative to 12pt
17pt 12pt 10pt 9pt 8pt 7pt 6pt 5pt (12pt compared to cmr 12pt)
cmr 83% 100% 109% 116% 120% 124% 130% 139% Computer Modern Roman 100%
cmti 100% 106% 112% 115% 122% Computer Modern Text Italic 94%
cmbx 100% 105% 108% 112% 117% 120% 123% Computer Modern Bold Extended 170%
cmtt 100% 109% 116% 120% Computer Modern Typewriter 100%
cmss 99% 100% 102% 109% 113% Computer Modern Sans Serif 120%

To the left is an example of the same word (taken from a font specimine sheet) printed at 3 different point sizes (8,12 and 24) and then scaled up to the same size. The most obvious difference is that the characters are proportionally wider at the smaller pointsizes. It is less apparent that the stems of the letters are different:
24pt 12pt 8pt
stem of the "n" (compared to 12pt) 89% 100% 117%
counter of the "n" (compared to 12pt) 104% 100% 89%
width of "originality" (compared to 12pt)     93% 100% 104%


SmallCaps

A SmallCaps font is made by scaling the capital letters to the x-height (so that they are the same height as lower case letters without ascendors) and then adjusting the stem widths so that they too will match stem widths of the lower case.

Italic

The Italic transformation contains at least four parts: A change in the letterforms of the lowercase letters, a skew, and a condensation and a narrowing of the vertical stems..
Italic Angle Condensation Stem width change
Computer Modern Text Italic 14º 91% 94%
Times New Roman 16º 100% 91%
Adobe Times 15 100% 92%

Letterform changes in Galliard:

Letterform changes in Caslon:
(These glyphs have been deskewed to display the shape transformation better.)

Cyrillic Letterform changes:
(These glyphs are also deskewed.)

This is not a complete list, but it shows most of the salient features of such a transformation.

Oblique

The Oblique transformation is a simple skew,
Computer Modern Slanted Sans Serif 9.5º
Arial Italic (actually an oblique) 12º
Adobe Helvetica Oblique 12º

Extended/Condensed

In these two transformations the stem width is held constant but the horizontal counter sizes and side bearings are increased (or decreased for condensed).