Minus sign and fraction line perfectly aligned

Question

The minus sign and the fraction line aren't perfectly aligned, probably due to the presence of brackets. So I've found a way to make them be, using \parbox

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\dfrac{N_{i}}{N_{0}} = \exp \bigg( \parbox[h][2cm][c]{4mm}{$-$} \dfrac{{E_i - E_0}}{KT} \bigg)
\end{equation}
\end{document}

Is there a more elegant way to achieve this?

Answer 1

The issue really is the restricted set of fonts in the original Computer Modern set, leaving 12pt a bit of a mix between 12pt design size fonts and 10pt design size, scaled to 12pt.

It would be possible to force scaled 10pt fonts everywhere but simpler is to use latin modern, which does have a more complete set at 12pt.

\documentclass[12pt]{article}
\usepackage{lmodern}
\usepackage{amsmath}
\begin{document}

\begin{equation}
  \frac{N_{i}}{N_{0}} = \exp \biggl(-\frac{{E_i - E_0}}{KT} \biggr)
\end{equation}
\end{document}