How to determine the true size of a font?

Question

A colleague of mine is submitting a research proposal to one of the UK research councils, whose guidelines stipulate a minimum font-size of 10pt. My colleague, who is of course using LaTeX, uses the amsart document class with the 10pt option (which, in fact, I think it's the default). Looking at the .log file one sees that the 10pt version of the fonts are indeed being loaded.

However word has come back that the proposal falls foul of the research council's guidelines because the font-size in the PDF file that my colleague submitted is actually 9.6pt! Alas, no information has been given as to how this font-size was determined.

Questions

1. When is 10pt not really 10pt?

2. And how can one determine the true font size of a LaTeX-generated PDF document?

Thanks in advance!

Added

This just in: it seems that the culprit was the default scaling of helvetica, which according to the PSNFSS2e documentation (PDF file) is smaller than 1.

This still leaves the second question.

Answer 1

PDFedit will be able tell you what the size of particular bit of text in a PDF document is.

Answer 2

Adobe Acrobat professional: Tools -> Advanced Editing -> Touchup text tool. Select text, right click -> Properties. Text tab, Font Size box.

Answer 3

There are several definitions of the word “point,” and LaTeX itself has two different units, the pt and the bp (for “big point”).

Since you say that’s a minimum size, the easiest solution is probably to load \documentclass[11pt].

With fontspec and a modern TeX engine, you have the option of setting \defaultfontfeatures{ Scale = MatchUppercase } and then loading your main font with \setmainfont[Scale = 1.042]. (Or 4.2% higher than whatever it’s at now.) This should scale your main font to the size the publisher requested, and scale all the other fonts in the document to the same height.

If you’re using 8-bit fonts, many legacy font packages support a scale= option.

Answer 4

Many documents include Scale=MatchLowercase or Scale=MatchUppercase as default font features with fontspec, which makes sense, except that this causes the package to scale the main font against the prior default (normally Latin Modern). To check what LaTeX considers to be the font size, you can use something like this:

\documentclass[12pt]{article}
\usepackage{fontspec}
\defaultfontfeatures{Scale=MatchLowercase}
% font will be rendered at 11.02771pt with the following line removed
\defaultfontfeatures[\rmfamily]{Ligatures=TeX,Scale=1}
\setmainfont{TeX Gyre Pagella}

\begin{document}

The quick fox --- \the\fontdimen6\font\relax

\end{document}

Answer 5

This question is related to many other questions dealing with "font size". I wrote this simple tex file for myself. I have taken out my (pure XeTeX) formatting commands so as to make it readable and changeable. See the attached PDF file where the font was Libertine Roman at a nominal point size of 12.5pt

Introductory material

When we speak of the point size of a classical (i.e. engraved in metal) this is a nominal value. Each character will have a different combination of height (total distance above the base line), depth (total distance below the base line) and width. Similarly in TeX if we define a font to have a size of 14.0 pt then 14.0 points is the nominal size. In TeX we can precisely determine the above values by looking at the bounding box of a letter. We do this by placing the letter, or letters, in a hbox and the using the command \the as applied to the \ht, \dp and \wd of the box.

Suppose that we are interested in the letter "g", which dips below the baseline. We first write:

\setbox0 \hbox{g}

and then determine the values as follows:

height = \the\ht0

depth =  \the\dp0

width =  \the\wd0

Here is the entire program:

\setbox0 \hbox{g}

\centerline {
height = \the\ht0
depth =  \the\dp0
width =  \the\wd0
                  }

We can also obtain the maximum range for a given nominal point size by placing the entire alphabet inside a hbox:

\setbox1 \hbox{abcdefghijklmnopqrstuvwxyz}
\centerline {
height = \the\ht1,\qq
depth =  \the\dp1,\qq
width =  \the\wd1
                  }

link 1 PDF output

link 2 original TEX file (plain XeTeX, the macro commands are available link to macro files if desired

Answer 6

You can copy fragment of the text from PDF viewer (I tried both Adobe and Foxit reader) and paste it to some text editor supporting copy / paste of formatted text (I an on Windows thus used Word). The text is normally pasted with formatting, thus font size can be seen as property of this text.