Postscript Autohint Interpolation Settings Question

Hi team,
I’m trying to find the best settings for postscript autohinting for a multiple masters font with two masters (hairline, black).

These are my current settings:

Hairline vertical stems: 10, 10
Black vertical stems: 177, 194

As you can see black master has two values for vertical stems since they are too far away from each other to be melted down to one value as the tutorial suggests (Hinting: PostScript Autohinting | Glyphs). Hairline instead would have only one value per v-stem but since the black masters has two per stem, I assume it is best to also have two per v-stem for the hairline master in order to create interpolated hints for generated instances. Am I correct?
Or can the hairline master have one value per v-stem only in order to have less values and black has two values per v-stem and autohinting would still work for generated instances?


That looks good. You are right that you need the same number of stems to be able to interpolate.

Perfect, thanks!

In this case, I would use only one V stem, in either master.

The difference between the two bold stems is so small, I cannot imagine the scenario where it would be acceptable to display them with a bigger difference (e.g. 3 vs. 4 pixels). But that is what you allow the renderer to do if you set up two different stems.

So I would use the more important of the two stems and discard the other. Or find a good average value, like 180 or 190.

Ok, I understand. Less is more. :slightly_smiling_face:
@mekkablue Now I’m curious: At what distance would you set up two different stem values if 17 units far is still too close?

There is no set distance. The question is if those to features should be allowed to have a different size in small sizes. So you could have one stem for lowercase and uppercase to allow the later to be heavier. But you probably don’t like to add two for strait and round stems as those shouldn’t be different by a whole pixel.

@GeorgSeifert True! So one value per stem then.
Thanks Georg!