customize reference to subfloat

Question

This script:

\documentclass{article}
\usepackage{graphicx}
\usepackage{subfig}
\begin{document}
See Fig. \ref{fig:exa}
\begin{figure}
  \centering
  \subfloat[example a]{
    \label{fig:exa}
    \includegraphics[width=0.5\textwidth]{example-image-a}
  }
  \subfloat[example b]{
    \label{fig:exb}
    \includegraphics[width=0.5\textwidth]{example-image-b}
  }
\end{figure}
\end{document}

renders output

How can I format the reference to subfloat as "Fig. 1(a)".