I have some uncertainties about the relationship between bearing and kerning. I'm working on the Italic of a font where, to express myself in a very practical way, I created in a subtable a "right" group with BDEFILNP. However I realized that the left bearing in these characters is different, so for example by setting the same kerning space there is more space between the glyphs of the AD couple and less space with the glyphs of the AL pair. Is this normal or does it mean that the width of the various glyphs is badly set? At this point I should change the left bearing so that all glyphs BDEFILNP have the same bearing space on the left or leave them as they are and work with kerning, but without creating a unitary class that includes the glyphs mentioned above? Thank you
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Would it not be more reasonable and convenient for kerning to set all glyphs with the same "left side" with the same bearing?
In that font/D and /L have respectively -36 end -37 LBearing.
Ok, I'll try some changes to bearing before taking care of the kerning
It seems to me that in IAI there is more space between IA respect than between IA
It's completely evident that in IMI and INI there is much more space between MI and NI
compared to the previous glyphs couple.
In cases like this have I to intervene by means of kerning, or changing bearing? Can this last solution present contraindications?
I'm inexperienced, but the logic of these numbers escapes me: 17,99?
Why bearing ofter is not symmetrical, even if the glyph is perfectly symmetrical like that of the letter N?
It' very interesting what you say about Italic sidebearings (all glyphs optically symmetrical either at the baseline, half way up the x-height, half way up the cap height, or somewhere in between), but what does it mean in more practical words? Is there a guide I can read?
Part 1 – Adventures in Space: Spacing
Part 2 – Adventures in Space: Kerning
Part 2.5 – Adventures in Space: Special Cases
Part 3 – Adventures in Space: Tracking
However, those articles enunciate more than anything else "philosophical" principles which, in theory, are already clear to me. It is known, however, that moving from theory to practice is not always painless.
For example, one of those articles states the principle that «the right bearing of an 'h' will be similar to the 'm' and 'n'». And in fact in a .pdf written in 10-12 pt body the spaces between the glyphs seem more or less the same.
But if I then check the RBearing of \m \n and \h for example in the GaramondPremierPro I find that the values are: 25 for \m, 28 for \n, 11 for \h. The same for ATFGaramond: 18 for \m, 24 for \n, 26 for \h. I do not think that these differences are the result of chance or inattention, but I can not identify the reasons.
Now I ask: would it not be more appropriate to set these values to an equal extent, which would make it possible to create simple and homogeneous classes of kerning?
In the font I'm working on to learn these procedures, do I have to keep the bearing as find it, which is different, or proceed to homologate it for similar glyphs?
In any case, it would be important for me to understand two things:
1) it is convenient to set all the characters with similar characteristics (for example \c \e and \o) in this case with a strictly equal LBearing, and to set all the characters with similar characteristics (as well as \E \B and \N) in this case with a strictly equal LBearing?
2) Is it convenient to set both the LBearing and the RBearing of the same glyph identical?
What font editor are you using? Most if not all can link to references when setting sidebearings, so for example you can set /B's LSB not to a number of units, but rather to match /H's. Then if you change /H's, /B's will change too. Probably wouldn't be a terrible idea to set all straight-sided letters to reference the same glyph as a starting point, and then use your eye to decide if letters like /I or /N should be unlinked and adjusted. Likewise, in many designs /c or /e may be linked to /o, and so on.
For sloped letters like italics, best for your sanity is to use a font editor that employs indicators of sidebearings that are slanted to a set italic angle. If that's the case then yes, symmetrical glyphs (sloped or not) can be set to identical sidebearings. You may find that your editor even allows the RSB of /H to be linked to its LSB.
As always with type design, automate where you can, but give your eye the final decision.
However, something something still escapes me.
I set, for exclusively experimental reasons, both LBearing and RBearing to 20 units to three glyphs. Here the result:
Now, even with the naked eye it is clear that the space between \i and \l is a bit larger than that between \h and \i. In this case, what's the reason? What am I wrong in calculating the spaces to be attributed to the bearing? There must be a method to calculate these distances exactly, I believe!
As George suggested above, distance between stems is a better starting point than distance between serif tips. But I don't know if FontForge enables setting sidebearings at a specific height.
@George
So, if I'd like to have an identical bearing, from what to what must I calculate?
What you want, in order to space glyphs systematically and compatibly across a family, is to establish what I call a 'spacing height' — typically slightly higher than half the x-height for a Latin type — at which to do measurements from stem edges rather than from extremes. This allows you to provide consistent visual rhythm between stems independent of the length of serifs, and independent of slant angle.
A last question: there is a method, an instrument or a calculation to measure accurately the space between the left and right extremes of a glyph after it has been applied the kerning?