[Tex/LaTex] Set font expansion so that distortion is not noticeable

font-expansionmicrotypetypography

In a comment to The kerning option of microtype Karl Karlsson writes:

Most of the typographers agree, that Font expansion distorts the font.
Personally, I see it, and I agree – the distortion is quite visible
for the trained reader.

I've always thought font expansion was great because it reduced hyphenation and I haven't noticed any distortion. The reason that I haven't noticed any distortion is probably because I've read documents on screen or draft/economy mode inkjet prints. When I recently got a document printed on a laser printer I noticed the distortion and it was irritating. The font I noticed it for is Latin Modern in 12 pt with the default font expansion settings. Before I only had documents printed on laser printer as two pages per paper (same font and font size) and then I did not notice any distortion.

In the microtype manual I read that the amount of font expansion can be configured by changing stretchability and shrinkability of a font via stretch and shrink and that their default value is 20 (ยง3.3). My question is: what is the greatest value for font expansion for which distortion is not noticeable when printing documents on a laser printer? I haven't got a laser printer so it's hard for me to test different values. Also, I'd appreciate any information on fonts for which distortion due to font expansion is rarely noticeable.

Best Answer

The following quote from section 9 of the microtype manual suggests that the package author was aware of potential negative effects of font expansion and viewed the default behaviour stretch=20 as sensible:

Expanding the fonts by more than 2%, i. e., setting a stretch limit of more than 20, should be justified by a typographically trained eye. If you are so lucky as to be in the possession of multiple instances of a Multiple Master font, you may set expansion limits to up to 4%.

Latin Modern (Computer Modern) -- and especially its design size of 12pt -- is a very "light" font, i.e., it has a high ratio of the width of the set of all lowercase letters, divided by the stem width (A short introduction to font characteristics). Therefore, it may well be that microtypes maximal expansion of +/-2% is less suited for Latin Modern than for "darker" fonts like Times.

In section 9.4 of The Elements of Typographic Style, Robert Bringhurst demonstrates (and by implication issues the blessing to) font expansion of +/-2%. (The book's text face is Minion Pro, apparently a "darker" font compared to Latin Modern.)

Related Question