What is the custom proportions field for?

In font info, there is an unavailable field labeled “Custom” under proportions. What is that for? Can I use it to add a third interpolation axis, such as contrast or optical size?

I always planed to add a third dimension for interpolation but never got the math right (thats why they are disabled). I either fix this or remove the buttons, soon.

Is there any documentation or tutorial for this Custom field? I couldn’t find anything. Thank you

The new handbook is coming along. But in the meantime, it’s works just like the other dimensions, The only difference being that you have to give it your own name, e.g. large and small instead of light and bold. And it is necessary for the color font. You can take a look in the layered color font tutorial.

OK, cool, thanks. I’ll experiment.

I had used this field but then took masters out, so I’d like to de-activate it. But the app won’t allow the value field to be empty now, even when the name is deleted from all masters. How to completely clear the Custom Proportion fields?

You need to have a number in each of the interpolation value fields. Set it to zero if not needed.