(I am a student in the TypeWest program so please forgive any basic questions.)
I have a question about metrics: Should the ascenders/descenders match the metrics we are using? For example: If my Ascender metric is 800, should the stem of the “b” touch/reach the 800 position?
I’ve seen various typefaces use different types of alignment and I’ve made my findings into a diagram below. You can right-click and "Open Image in New Tab" to make the image bigger.
I’d love to know about best practices since not “reaching” the metric value leaves more space. Let me know if this question is confusing and I can try to clarify.
(I am using a 1000 UPM grid by the way.)
Especially true for things like whether your ascenders (of the actual glyphs) are higher than your caps and by how much.
Afterwards, you can scale glyphs, or change the em, if the relationship to “standard” sizes is out of whack. Obviously best to figure this out before you have too many glyphs!
And then… there isn’t just one ascender metric value (and descender, etc.), but technically three, in the font data.
Google Fonts’ detailed advice about setting these values can be found here: https://github.com/googlefonts/gf-docs/blob/main/VerticalMetrics/README.md
That is not the ONLY possible scheme, but it is at least one of the reasonably sane ones.
Should I start drawing first and add metrics after? Or should I set up some general metrics before drawing and modify them at the end?
I've been setting up my metrics first and drawing to fit them but I don't know if that's the best way to do things.
See also this detailed thread on vertical metrics.
Almost surely you will change these early designs, but here you have a start point with room for diacritics. And please note that this sum is a possible approach, not a definitive rule. Many designers prefer to work with different criteria.
Most fonts are drawn with equal values to ascender and descender. Some, like me, prefer to make descenders a bit shorter than ascenders. It's a design choice, not a rule.
Another item is the existence of stacked diacritics in some languages. I do not consider them in the vertical metrics because it compromises the design too much. And people who use these languages can avoid line collision just increasing the text leading.
Finally, all what I wrote is good for Latin, Greek, and Cyrillic scripts. But for other scripts the needs are different and you need other criteria.
Even when making specialist fonts that support unusual notation systems and vertical stacks, I try to avoid making the basic letter shapes too small on the em, and instead accommodate the taller space requirements elsewhere in the vertical metrics. I try to design my basic letters relative to the em such that at e.g. 12pt the size of the letters is within a conventional range of what people think of as 12pt visual size.
Your (d) option seems reasonable given the historic sources and your desire to be faithful to them and what they represent about the way roman and italic typefaces were combined. I suppose the question is really what experience you want users to have, and whether it is important to cater to expectations based on established conventions of harmonised type families?
From your illustration, I would say that the italic looks quite massive relative to the roman—not only in terms of the extenders but also the x-height and some stem weights—, so rather than shortening the ascenders and descenders, you could perhaps keep the design as it is, but scale it completely to harmonise with the proportions of the roman.
[I often make my italic x-height slightly shorter than that of the roman, because the slanted strokes are longer than the vertical ones, and create the optical effect of italic x-height looking larger than the roman when actually the same size.]
I can report that the strong majority of typefaces have a cap height that is in the range of 60–75% of the em. URW standardized the cap height of all their (non-knockoff) typefaces at exactly 2/3 of the em, which was also around the average of all the other typefaces I tested.
The trend in later typefaces is to be on the lower end of that range, so typical numbers for more recent typefaces might be more like 60–67% of the em.
Diacritics above ascender are very near to the diacritics above uppercases in traditional design. This small difference will not make letters unusually small. Even if the font has no support for languages with diacritics above the ascenders, the suggestion I gave will allow room for UC diacritics plus a small free space.
With regard to diacritics above uppercase letters, I typically allow these to extend beyond the UPM height, because making them fit does require ‘casting the letters small on the body’. For example, the red lines in this image show the UPM height in the Brill types, and that is an example of a design that I deliberately made slightly shorter than usual on the body because I knew it would frequently be used with a lot of diacritics:
This, from Constantia, is more typical of what I do for a general purpose text font, with the body height close to the lowercase ascender + descender:
* Yes, it is possible to work with fractional coordinates, but a) this is messy to work with and b) you end up having to round elsewhere in the production chain for some font formats, so I always work in full UPM coordinate integers.