Interpolating MM across optical axis

Hi all,

I’m a design student in the South-West of England. I’ve been using Glyphs App to design my first ever typeface design which I feel has been a resounding success. The question that brings me to the forum is a fairly basic one; having set up two extreme multiple master variants I’d like to know whether or not it is possible to interpolate between the two variants across different optical sizes of the typeface in Glyphs App.

Any reply would be massively appreciated, I’ve searched high and low but found no answer as of yet!


if the outlines are compatible you can interpolate anything. Did you read the Multiple Master tutorials?

HI Georg,
Yes I’ve read the tutorials pretty extensively. Perhaps I’m not explaining my intentions fully? I have designed two variations of my typeface. What I would like to do is have the initial style graduate to the second more extreme variant as the pt size of the typeface increases in publishing software.

I know this can be achieved by creating a multiple master along an optical axis and then by selecting the little used ‘automatically use correct optical size’ option in Adobe InDesign. What I’d like to know is; is this possible specifically in Glyphs App and how to assign my two variations (and interpolations) to the intended point sizes?

Many thanks,

Just to clarify further:

“Some multiple master fonts include an optical size axis, which lets you use a font specifically designed for optimal readability at a particular size. Generally, the optical size for a smaller font, such as 10 point, is designed with heavier serifs and stems, wider characters, less contrast between thick and thin lines, taller x height, and looser spacing between letters than the optical size for a larger font, such as 72 point.” 29a.html#WSa285fff53dea4f8617383751001ea8cb3f-6e18a


I understand. Your question mixed to different things. You wanted to know if it is possible to set the size range for a font. That has nothing to do where you got the instance from (if interpolated or drawn manually).

Setting the size information is not jet possible in Glyphs for more then one instance. It would be set as described here:

I will have a look on how to implement it properly.

Thanks Georg.

Perhaps I myself am a little confused. Research I have done into Opentype ‘size’ information shows that it is totally unrecognised by all desktop publishing software. What I’m now struggling to understand is, if Adobe InDesign features a ‘use correct optical size’ option then how does one go about prepare a typeface to be used in this manner?

I’m trying to automate changes in the typeface when typeset at different optical sizes.


This video and the below comments show my exact intention but I cannot for the life of me find documentation on how to do this!

The solution that is used for the demo in the video is not supported by Glyphs. It uses the long gone PostScript-Multiple Master fonts.

Thanks Georg, being inexperienced I wasn’t aware of a differentiation between the Glyphs Multiple Master and the Postscript-Multiple Master that you speak of.

One final question; are you aware of any type design software still able to generate these Postscript-Multiple Master files and would I be able to export my Glyphs masters and then subsequently import them to this software.

Thanks so much for your time and support, it’s massively appreciated!

You can create MM fonts with FontLab Studio. There are import macros for Glyphs files on but I would not recommend producing MM fonts to someone inexperienced. Don’t say I didn’t warn you.

Why do you need this?

I just got a response in typedrawers. So it seems that Indesign CC can use old style MM fonts to display size specific fonts (as seen in the video).

And yes, the term Multiple Master is misleading but it’s so commonly used that it is difficult to establish something else.

I have a copy of Fontographer 5.0 so should be able to import my Glyphs masters as Opentype files and then create PST1 MM in Fontographer. I understand I may have been a little overambitious in what I aim to do especially for my first type design project but as it currently stands I have a set of compatible master outlines for linear interpolation and so feel as though I’ve already surmounted the hardest part! I may be wrong in that assumption though…

@Mekkablue you mentioned on Twitter that there was a way to ‘add the optical size feature manually’ is this still the case? I know that it is possible using the OpenType ‘size’ tag but also that this is currently unsupported in all desktop publishing software!

@Georg If my research is correct then the ‘automatically use correct optical size’ preference in Adobe InDesign actually extends much farther back than just in CC. I think that old style Postscript MM fonts should be supported at least back to CS5

Project is for BA Hons Graphic Design at the University of the West of England

Thanks again,

You can add the feature, but there is no app that uses it so just forget about it.

I had thought it was already implemented, but I stand corrected.

So, what exactly is the problem with generating size-specific instances, like Caption, Small Text, Regular, Subhead, Display? Or naming them after their intended point size?

The automatic change is just for the show anyway, and in practice more in the way than supportive. Because pretty often, you need a small design size at a large point size, especially at higher viewing distances (think signs for instance).


Technically there is no problem with doing it in that manner and in fact I am aware that this is certainly possible, more supportive and much simpler to do!

The reason I wanted to do things in an automated manner was for the most part because the project is more high-concept than based on typographically sound principals. I’m looking for the typeface glyphs to distort and become less legible at larger optical sizes, at the interval of each individual point size. This is for conceptual reasons based around the subject matter of the original type design. Additionally as far as I could make out such an automated design is an extreme rarity and so having something that responds in real time to user interaction and engagement would have been incredibly interesting as a project.

As it currently stands I’ve managed to convert my Glyphs outlines to a PST1 MM file in Fontographer, as far as I can make it out it should now only be a simple case of creating interpolation instances in TransType 4 and then using Adobe Indesign’s ‘Automatically Use Correct Optical Size’ option. From this point my dream may soon become a reality!

Thanks a lot to both you and Georg for the help provided, the support here is unparalleled. I’ll endeavour to keep you updated should I be able to bring this interesting project to fruition!