Opsz values for named instances in variable font

If I am setting up the exports for variable font with multiple axis, one of which is opsz, what value is recommended to use for the optical size of the named instances?

I assumed it should match the optical size value of the master selected for the Variable Font Origin, but my exported variable font file was suddenly snapping to another point in the design-space when the slider was moved to the end of an axis. (Initially I thought this was an inDesign bug, the behaviour is the same in Axis-Praxis)

I’ve tried a few different combinations of Variable Font Origin and which opsz values for named instances, but can’t seem to fix it.

It’s also a possibility that the issue is because of something in the axis mapping, but I’ve double checked this values and can’t find any errors there.

Any ideas?

This is the official recommendation:

Which app, which OS?

macOS used to have a bug related to opsz, visible e.g. in Safari. IIRC there’s a chapter about it in the variable font tutorial.

Hi Rainer, thanks for your response.

The snapping was happening in both InDesign 2022 and using Axis-Praxis on Chrome. Both on a Mac running Catalina (10.15.7). The variable font was exported using Glyphs 3 (3.0.4).

I can’t see anything in the spec which would solve my problem unfortunately.

I have since exported the variable font again without and named instances, and the snapping behaviour doesn’t happen any more. So I can rule out any having made an errors with the axis mapping.

I would now guess that the issue is down to which instances I am activating when the variable font is exported. From a user point of view, I would like to keep the list of instances as small as possible, ideally just the weights with ‘normal’ widths. Indesign (or whatever other app) can then take care of the opsz and the user can tweak the width up or down themselves.

I am guessing what I should be doing instead is, at a minimum, exporting an instance on each of the 8 corners of the design space? Kind of annoying as those are going to be much less often used compared to the normal weights. Of course, I could export more instances, but then the list of instances to use becomes difficult to use.

I will do some more tests and report back.

Try with the latest beta.