I thought the hyphen was supposed to be approximately the width of a lowercase i (including sidebearings). However, when I look at various typefaces, I see that this varies considerably (some hyphens are longer, and others are shorter).
Bringhurst says the hyphen is now standardized to a quarter em, for what that's worth.
It seems clear to me that with condensed or expanded designs, such an em-based standard isn't going to work. But Bringhurst is usually talking about text types.
I’ve read that hyphen is a quarter em, endash is half em, and emdash is equal to an em (which IMHO is often too much, as you can see in Adobe Caslon). I’d say it depends of other proportions, most importantly x-height and width of the letters.
In former times, the drawing sizes of typefaces were much more standardized than today. Looking back at Monotype casters, each font had a "set width" that indicated the width of 18 spacing units (one horizontal em) at a certain font size. For normal proportions, the "set" equaled the font size. For a condensed font, the set could for example be 10, while the font height (apparent size) would be 14 pt. Basically this meant the machine operated like it would for a 10 point font, just the letters would be taller than normal.
The definitions of the widths of hyphens, en- and em-dash would make much more sense in connection to those horizontal ems than to the vertical font size.
Bringhurst says the hyphen is now standardized to a quarter em, for what that's worth.
Hmm. I’ve never made a hyphen as narrow as a quarter em. And I just checked a handful of Font Bureau fonts I’ve worked on production for and couldn’t find one either.
For any style of font, I have understood that somekind of a rule is that en-dash width is width of /n and em-dash width of /m. I wonder where I got this "rule".
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On the side note, Any idea if this information is indeed recommended for determining vertical metrics? https://www.glyphsapp.com/tutorials/vertical-metrics
Perhaps the width can be adjusted "to taste"?
It seems clear to me that with condensed or expanded designs, such an em-based standard isn't going to work. But Bringhurst is usually talking about text types.
The definitions of the widths of hyphens, en- and em-dash would make much more sense in connection to those horizontal ems than to the vertical font size.