LSB and RSB Interpolation Issue


I am writing to you all today because I have an interpolation issue (possibly a software bug).

I am creating a font family with multiple weights. The glyphs with flat edges on both sides have LSB and RSB values of 60 units for the lightest weight. The heaviest version of my font uses 30 units for left and right flat edges. Letters like “T” have consistent side bearings for both weight extremes (10 units on both sides).

If I view my font in an intermediate weight, the distance between a flat edge and the left side of the “T” is greater than the distance to a flat edge from the right of the “T.”

Any help troubleshooting would be much appreciated!


How much difference do you see?

Not a lot but the difference is definitely not the same.

Here is a screenshot example of the intermediate weight. The sidebearings should result in equal spacing around the “T” but it doesn’t.

Lightest Weight: LSB (60-A-60) RSB, LSB (10-T-10) RSB, LSB (60-E-60) RSB
heavest Weight: LSB (30-A-30) RSB, LSB (10-T-10) RSB, LSB (30-E-25) RSB

Screenshot 2024-02-23 at 2.18.27 PM

Do you have any kerning or intermediate layers in your file?

Is the above screenshot from the Glyphs preview panel?

1 Like

No kerning right now. Yes on Intermediate layers. I’ll check to see if that’s the culprit.

Yes, the screenshot is from the preview panel.

Intermediate layers on the “E” is what was causing the issue. Thank you for your suggestion.