Character space, line space

[Rainer1]

Hello,

please, does anybody know to which base value line space or character space are related to?
The input value is 1, 5 10 or 20 etc. %. But of what base value?

I can´t find any information in Affinity Help. In Indesign for example the base is divided into
1000 parts of a square sized to the font size one works with at the moment.

Sometimes information in Affinity Publisher Help is a little bit poor. Is there a possibility
to get access to more specific information in an easy way. I already visited the official
Affinity Tutorials and other sources. Its hard to find those informations.

Thanks in advance for your reply.
Rainer

[walt.farrell]

38 minutes ago, Rainer1 said:

which base value line space or character space

I'm not sure which settings you're referring to. Can you share a screenshot to confirm which ones you're asking about?

I think my confusion may arise because I'm more used to seeing what I call line spacing defined in points, not % values. Though it can be % values, so maybe that is what you're asking about. In that case it's listed as % of "height", presumably the letter height specified in the font.

[Rainer1]

Hi Walt,

thank you for your response. I ment especially the character space.
Meanwhile I did a test by placing a rectangle, width 10 pt, on top of
a text line with 10 pt character height. Aligned to the right boarder
of a character. After that I first decreased the character space between
this character and the following until the characters get touched.

Result: value -150 %.

Then  increased the character space again until the left boarder of
the displaced character reached the right boarder of the rectangle.

Result: 850 %.

Both added = 1000 %.
So, like in Indesign, the base value (height of the character) is
presumably defined with 1000%. For me this knowledge is
important. As a graphic designer and typographer I have to work
with proper values.

Thanks again for your answer.
Rainer

[Mark Oehlschlager]

Line spacing (which most software interprets to mean the distance between baselines) is usually expressed in points. A typical type specification like 12/14 Garamond for body text is understood to mean 12 point Garamond with an extra 2 points of leading for total interline spacing of 14 points.

Letterspacing or kerning is traditionally expressed in 1000ths of an em (the body size of the type used, e.g. 12 point Garamond). 

I don't understand the 0/00 symbol in the Publisher character panel, but the values one plugs into the kerning field are in fact 1000ths of an em (i.e., for 12 point type, with your cursor inserted between two letters in a word, if you enter 1,000 into the kerning field of the character panel, you will insert 12 points of space between the letters).

Postscript: Just in case there is any confusion in the matter, also remember that the letter forms in a digital font all fit within a digital bounding box with small margins (side bearings) between the letter form and the bounding box. This prevents neighboring letters from touching. Moreover, fonts are designed to have prescribed kerning (spacing) between specific pairs of letters, encoded in kerning tables within the font. So, in addition to whatever letterspacing changes you make between letters (adding or removing space), the side bearings of the letterforms will be included in the resulting space.

[R C-R]

14 hours ago, Mark Oehlschlager said:

I don't understand the 0/00 symbol in the Publisher character panel ...

‰ is the Unicode Character 'PER MILLE SIGN' (U+2030). Per mille means "for or out of every 1000."

[R C-R]

15 hours ago, Rainer1 said:

Meanwhile I did a test by placing a rectangle, width 10 pt, on top of a text line with 10 pt character height.

Adding slightly to what Mark said, note that font size, often specified as a point size (for example as "12 point Garamond"), & character height are not the same thing. There are several different design factors that determine a character's height within a font. See for example the x-height Wikipedia article for a brief(ish) discussion about that.

As the point size link mentions, at one time "point size" referred to the size of the of metal blocks with the character cast onto its top, like the one shown in the photo in the Type-founding section of another Wikipedia article. (Trivia: "upper case" & "lower case" came from the cases or drawers used to store these pieces.)

Should you be wondering about the different point size definitions, I am almost certain that internally Affinity uses what is sometimes called the "Desktop Publishing Point." Blame the creators of Adobe Postscript for that.

Anyway, the point (no pun intended) of all this is that a font's point size alone doesn't say much about its line or character spacing ... or even about its character sizes.