# How do I get a light math font?

Here is my problem. I'm using the font sourceserifpro, with the "extralight" mode, and I'm getting this as a result:

As you may see, the math formulas appear a bit darker than the rest of the text, as if they were bold. Whence my question: is it possible to make the math formulas lighter or brighter ?

(A very naive idea would be to make these formulas grey instead of black — automatically. A naive idea would be to make them less "opaque", i.e. more "transparent" — again automatically). But I don't know any way of "thinning" those math symbols.

I hope that my question is clear and that I will get some... enlightning answers!

Here is the MWE:

\documentclass{report}
\usepackage[default,extralight]{sourceserifpro}

\begin{document}
Given elements $a_1, ..., a_n \in k$, we denote by $\mathrm{diag}(a_1, ..., a_n) \in M_n(k)$
the diagonal matrix whose $(i,j)$-th entry
is $a_i \delta_{i,j}$ for any $1 \leq i,j \leq n$.
\end{document}

• You cannot make the font thinner. The outlines are fixed. You could grab the Metafont sources of Computer Modern and produce your own fonts with lighter weight, but this is probably an effort you don't want to take. – Henri Menke Jan 4 '18 at 22:51
• @HenriMenke : in that case, what about the (very) naive ideas I proposed in my question? – Watson Jan 4 '18 at 23:08
• this question Is it possible to use custom font as math font?, which appeared earlier today, may be useful for letters and digits, but i'm at a loss what to do about symbols. maybe someone else has some good ideas. – barbara beeton Jan 4 '18 at 23:12
• You might try the xcolor package and \color{lightgray}. – John Kormylo Jan 5 '18 at 16:26
• @JohnKormylo : yes, but is it possible to have "lightgray" activated automatically for all the math formulas in the document (instead of adding the command manually at each formula...)? – Watson Jan 5 '18 at 18:49

You can color the math font automatically if you are willing to use unicode-math with LuaLaTeX (better don't use XeLaTeX).

\documentclass{report}
\usepackage{xcolor}
Given elements $a_1, ..., a_n \in k$, we denote by $\mathrm{diag}(a_1, ..., a_n) \in M_n(k)$
the diagonal matrix whose $(i,j)$-th entry
is $a_i \delta_{i,j}$ for any $1 \leq i,j \leq n$.