All caps descender setting

Jani Paavola

What is the common practice setting (TypoDescender and hhea) descenders in all caps font?
When it should be "lowest a-z letter", in all caps font that wouldn't be much. Go with it or something else?

John Hudson

If your caps are scaled such that they correspond to typical height relative to the em body (nominal text size), then it makes sense to assign vertical metrics that are similarly typical. In other words, you can either presume a typical vertical arrangement in which the baseline is somewhere around 25% of the height of the em, or you can imagine what your lowercase ascender and descender heights would be if your design were to include lowercase letters.

In metal type, all-caps designs were sometimes cast larger on the body than typical text caps, so the baseline was lower on the em body. That is also an option, but you still want some descender space to accommodate e.g. cedilla or other below-letter marks.

Jani Paavola

I'll add some descender value as if lowercase existed, makes sense. Thank you John! 

John Savard

The letter Q descends below the baseline, and in some typefaces, so does the letter J. So one doesn't have to go to foreign languages for the cedilla to see the need for some descender space.

But reduced descender space makes sense for a titling font; if it's going to be mixed with other text, one needs a baseline that lines up. However, with digital type, that isn't an issue, I thought: if typefaces or styles with different descender space in the same size of character cell vertically are mixed, the line just takes up more vertical space, since the characters are lined up by the baseline, not by the top and bottom of the character cell.

Ray Larabie

I usually set it to the ogonek and section symbol.