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# Font Info – Masters

While information about the designed masters (the input) is set under ‘Masters’, the ‘Instances’ tab contains information about each instance that will be generated when fonts are exported (the output). Use the plus and minus buttons to add and remove masters, and the ‘Add’ button to add any open single-master font as a master to the current font. You can add the font to itself to have two identical masters to start from.

Standard stems and alignment zones are necessary to optimize the font’s rendering on screen, where these characteristics may be represented by only a few pixels. Small deviations in the drawing can – after rounding to the pixel grid – result in considerable differences. Stems should have a uniform thickness. Alignment zones help create an even vertical alignment by overshoot suppression. The values entered here are crucial for the autohinting process when the font is being exported.

All values will be interpolated if entered in the same order throughout all masters. You can edit several masters at once after you Shift-click or Cmd-click the master names in the list on the left.

## Proportions: Weight and Width

The values in these two pop-ups affect only the toolbar icons. The values for the actual interpolation are set under ‘Instances’. For more information about this, see the Multiple Master chapter.

## Metrics

The vertical metrics have an impact on the line height, and serve as a guideline in the editing window. Glyphs will calculate the vertical metrics in the OS/2 and hhea tables from these values.

Also, Glyphs is able to find alignment zones (see below) automatically if you first enter correct vertical metrics: ascender, cap height, x-height, descender, perhaps also a smallCapHeight in the Custom Parameters.

When determining these values, ignore the overshoot. So, for instance, if you have the choice between various values for the x-height, say 490, 496 and 502, you want the one closest to your baseline, i.e. 490.

## Stems

If you enter good values for your standard stems, the autohinter will find those stems in your letters and put a hint on them. Try to find values as representative as possible, separated by a comma.

For vertical stems, consider the widths of your lowercase and uppercase stems and bowls. It’s a good idea to measure the stem width of a lowercase i and an uppercase I, and the distance between the extremum points in the bowls of lowercase c and uppercase C. For horizontal stems, consider the bars of t and E, the upper bowls of o and O, and the thickness your serifs if you have any.

Usually, not more than two stem values (for either horizontal or vertical stems) are necessary. If a few potential values are very close to each other, pick the most representative one, e.g. if you get measurements of 20, 21, 23, 43, 44 and 45 for your horizontal parts in your glyphs, then just enter 21 and 44 as your horizontal stems.

## Alignment Zones

An alignment zone must encompass anything that should later be aligned at a low resolution. For instance, the upper edge of the crossbar of t, the upper edge of x and the highest extremum of o, they should be inside the alignment zone for the x-height. However, the size of an alignment zone must not exceed 25 (or –25 for bottom zones), and there must be at least one unit between any two alignment zones.

After you have set the Metrics properly, you can click the grey circle to let Glyphs find the alignment zones for you. Glyphs will then reduplicate the heights of the vertical metrics you entered in the Metrics field as the positions of the zones. It also respects the ‘smallCapHeight’ custom parameter if present. And it will try to guess the size of the alignment zones by measuring certain key glyphs in the font. If it cannot find any glyphs to measure, the sizes default to 16 for top zones, –16 for the descender zone and –15 for the baseline zone. It is a good idea to double check if your most important glyphs do end inside the alignment zones.

For a more detailed discussion of stems and zones, see the Hinting chapter.

### Related Topics

Font Info – Masters Custom Parameters

Font Info