Different interpolation value for some glyphs only

Further to a similar post by Mark Simonson back in 2015, I have a font in whose Medium weight the caps are a bit heavy. It would be vey useful if I could visually shift specific glyphs heavier/lighter through the ‘design space’ (like a variable font) while in context with the lower case that doesn’t change weight, then save those values so on export those chosen glyphs export at a different value.

A workaround would be to export a font at the desired new weight, then cut and paste all the relevant glyphs back into the original font, but the font I’m trying to adjust has too many axes to make this practicable (and the thought of all that repetitive cut/paste is far too depressing). And you’d need to know precisely what weight value was required beforehand, which you don’t.

I’ve found that simply adding/removing weight to the Medium is not the same as shifting it forward and back trough the weight interpolation and needs lots of manual fixing, so again isn’t practicable.

Does a plug-in that does this exist? If not, does anyone fancy writing a write a plug-in? Happy to contribute some £££ as it’d save me a good few days work.

Thanks all!

Should that work for static instances or variable fonts?

Hi Georg - in this case, static fonts (but I’d assume it could be made to work for variable fonts too). Note that the adjusted weight of the Medium would need to interpolate as normal, ie the weights either side would be proportionally adjusted too, so it’d not be a case of just changing the Medium weight’s weight in isolation, or having to figure out and input adjusted weights for other exported weights too.

I’d imagine it would also be useful for adjusting the weight of small caps and superior/inferior numbers

Sounds to me like the RMX Scaler.

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Thanks, Florian. Unfortunately what that would do in this instance is take weight off in the same manner as the “offset curve” function, which as I say needs quite a bit of manual adjustment. The benefit of moving specific glyphs back/forward through the weight axis is that as well as weight, all other variables - sidebearings, kerning etc - will adjust as needed automatically. And having it as something that happens on export means there is no tweaking of glyphs at all.

The RMX Scaler does no do the same thing as Offset Curve; instead, it uses the masters that you have provided to interpolate the outlines to a different point in the designspace.

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in 2005 I built a variable demo font (MM) with 4 different interpolation curves to be used with different glyph topologies or glyph groups to tackle color problems. It works fine, and should be much easier with the tools of today, but it is much more practical to insert extra masters for those medium capitals.
With different interpolation values, unexpected things might happen. E.g. if your x-height varies between thin and thick, then different interpolation values will result in different x-heights and overshoots. Of course we can build a system where such values (like x-height and overshoots) are fixed before interpolation, or parametrised, as already existed in the brilliant Font Chameleon in the 90s, but I would rather make some intermediates and focus on the design.

Thanks, Lucas. This does have an existing Medium master, so the chances of weird things happening (as they might interpolating with just the extrema) I assume are small. It’s a small weight adjustment - maybe 6-10 units - but ideally needs immediate visual feedback to perfect. Florian - I’ll take another look at RMX Scaler. I may have it already - I use RMX Harmoniser a fair amount (thanks, Tim!)