tl;dr What factors (i.e. intended use, design style, etc) inform the design of these glyphs and are there any standards?
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Long version (my apologies in advance for the length! Footnotes in the next post as post is too long)
Why does the height alignment of superior figures vary²
so much between typefaces — is it to do with the anticipated uses or stylistic preference? Or lack of standard practise? I've seen the top of superior figures commonly aligned:
- Slightly above ascender height:
- Between the caps height and ascender height:
- With the ascender height:
- With the lining figure height:
(There's more variation depending on whether numerals are ranging, lining, hybrid, slightly-less-than-cap-height and also whether the ascender height matches the cap-height, etc).
Ordinals / Superior letters
Furthermore, how should ordinals (superior letters) be designed/aligned? Most commonly, I've seen typefaces that align:
- The x-height of ordinals lower than top of lining figures and baseline of ordinals below baseline of superscript figures³:
(PF Din Display)
- X-height of ordinals with lining figure height (also cap height):
b. variation where x-height of ordinals is aligned to the ascender height, when ascender > cap height:
- Cap-height (or ascender) of ordinals aligned to top of ascender:
- Baseline of ordinals with baseline of superior figures:
The x-height of ordinals are also aligned to lining figures
Brill does this too quite neatly as it aligns baseline and cap-height of ordinals to fit the superscript figures.
(Many other variations exist where more than one of these methods are true, and different ways of defining the same kind of the alignment are possible too)
I've only seen either the baseline of inferior figures aligned to the baseline, or just below.
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Conclusion: What's typographically correct, or appropriate depending on the intended use? What's plain wrong?