How to make bold text more visible

Question

I designed a T-shirt in OpenOffice and wasn't happy with the rendering of a lower case Gamma. I tried doing it in LaTeX, and neither the formula nor the text is as visible as the OpenOffice version. The markup I'm using is:

\documentclass{article}
\usepackage{bm}
\usepackage[paperheight=10in,paperwidth=10in,top=0.75in, bottom=0in, left=0in, right=0in]{geometry}
\usepackage{graphicx}
\begin{document}
\pagestyle{empty}

\vspace{.5in}

\begin{center}
 {\Huge \bfseries Which part of}
\end{center}

\vspace{1.75in}

 {\Huge
   \[
     \bm{(\gamma^{\mu } (i\hbar \partial _{\mu } - {\frac {e}{c}}A_{\mu })-mc) \psi =0}
   \]
 }

\vspace{1.75in}

\begin{center}
 {\Huge \bfseries don't you understand?}
\end{center}
\end{document}

I tried

\documentclass{article}
\usepackage{unicode-math}
\usepackage[paperheight=10in,paperwidth=10in,top=0.75in, bottom=0in, left=0in, right=0in]{geometry}
\usepackage{graphicx}

\usepackage{newcomputermodern}

\setmainfont{NewCMMath-Book.otf}[
  version=bold,
  FakeBold=2.0,
  FakeStretch = 1.1 ]

\setmathfont{NewCMMath-Book.otf}[
  version=bold,
  FakeBold=2.0,
  FakeStretch = 1.1 ]

\pagestyle{empty}
\begin{document}

\vspace{.5in}

\begin{center}
 {\Huge \bfseries Which part of}
\end{center}

\vspace{1.75in}

 {\Huge
   \[
      \boldsymbol{\gamma^{\mu } (i\hbar \partial _{\mu } - {\frac {e}{c}}A_{\mu })-mc) \psi =0}
   \]
 }

\vspace{1.75in}

and got

shmuel@linux-gn5l:~> latexmk -xelatex ~/Documents/Dirac
Rc files read:
  /etc/texmf/latexmk/latexmk.conf
Latexmk: This is Latexmk, John Collins, 17 Apr. 2020, version: 4.69a.
Latexmk: applying rule 'xelatex'...
Rule 'xelatex': The following rules & subrules became out-of-date:
      'xelatex'
------------
Run number 1 of rule 'xelatex'
------------
------------
Running 'xelatex -no-pdf -recorder  "/home/shmuel/Documents/Dirac.tex"'
------------
This is XeTeX, Version 3.14159265-2.6-0.999991 (TeX Live 2019/TeX Live for opensuse.org) (preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
(/home/shmuel/Documents/Dirac.tex
LaTeX2e 
(/usr/share/texmf/tex/latex/base/article.cls
Document Class: article 2018/09/03 v1.4i Standard LaTeX document class
(/usr/share/texmf/tex/latex/base/size10.clo))
(/usr/share/texmf/tex/latex/unicode-math/unicode-math.sty
(/usr/share/texmf/tex/generic/iftex/ifxetex.sty
(/usr/share/texmf/tex/generic/iftex/iftex.sty))
(/usr/share/texmf/tex/generic/iftex/ifluatex.sty)
(/usr/share/texmf/tex/latex/l3kernel/expl3.sty
(/usr/share/texmf/tex/latex/l3kernel/expl3-code.tex
(/usr/share/texmf/tex/latex/l3kernel/l3deprecation.def))
(/usr/share/texmf/tex/latex/l3backend/l3backend-xdvipdfmx.def))
(/usr/share/texmf/tex/latex/ucharcat/ucharcat.sty)
(/usr/share/texmf/tex/latex/l3packages/xparse/xparse.sty)
(/usr/share/texmf/tex/latex/l3packages/l3keys2e/l3keys2e.sty)
(/usr/share/texmf/tex/latex/fontspec/fontspec.sty
(/usr/share/texmf/tex/latex/fontspec/fontspec-xetex.sty
(/usr/share/texmf/tex/latex/base/fontenc.sty
(/usr/share/texmf/tex/latex/base/tuenc.def))
(/usr/share/texmf/tex/latex/fontspec/fontspec.cfg)
! Undefined control sequence.
 \LaTeX3 error: 
                           Erroneous variable \c__fontspec_shape_n_n_tl used!
l.3806 \emfontdeclare{ \emshape, \eminnershape }
                                                
?   

Answer 1

That’s the bold font of Computer Modern. If you switch to LuaLaTeX or XeLaTeX, and you really want to do this to Computer Modern, you can use fontspec options to thicken and stretch the math font:

\documentclass{article}
\usepackage{unicode-math}
\usepackage[paperheight=10in,paperwidth=10in,top=0.75in, bottom=0in, left=0in, right=0in]{geometry}
\usepackage{graphicx}

\usepackage{newcomputermodern}
\setmathfont{NewCMMath-Book.otf}[
  version=bold,
  FakeBold=2.0,
  FakeStretch = 1.1 ]

\pagestyle{empty}
\begin{document}

\vspace{.5in}

\begin{center}
 {\Huge \bfseries Which part of}
\end{center}

\vspace{1.75in}

 {\Huge
   \[
      \boldsymbol{\gamma^{\mu } (i\hbar \partial _{\mu } - {\frac {e}{c}}A_{\mu })-mc) \psi =0}
   \]
 }

\vspace{1.75in}

\begin{center}
 {\Huge \bfseries don't you understand?}
\end{center}
\end{document}