Caption sub-level within minipage

I have this code:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[margin=2.5cm, showframe]{geometry}
\usepackage{graphicx}
\usepackage{lipsum}
\usepackage[skip=0.33\baselineskip]{caption}
\captionsetup[figure]{
font=bf,
size=normalsize,
justification=centerlast,
%labelsep=newline
}
\begin{document}
\newcommand{\figurewidth}{0.95}
\newcommand{\figureheight}{0.375}
\begin{figure}[ht]
\centering
\begin{minipage}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{frog.jpg}
\caption{The first frog}
\end{minipage}%
\begin{minipage}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{frog.jpg}
\caption{The second frog}
\end{minipage}
\centering
\begin{minipage}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{frog.jpg}
\caption{The third frog}
\end{minipage}%
\begin{minipage}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{frog.jpg}
\caption{The fourth frog}
\end{minipage}
\vspace{2ex}
\caption{A couple of frogs}
\parbox{\linewidth}{\small\lipsum[1]\vspace{2ex}}
\end{figure}
\end{document}


which produces this output:

I have two issues:

(i) Is is possible to add a small amount of vertical space between the top (Figure 1 and 2) and the bottom (Figure 3 and 4)?

(ii) Is it possible to create a sub-level within the minipage environment? Say the overall page/figure is labeled "Figure 5: A couple of frogs", then I would like to name the individual frogs something like: "Panel 5.A: The first frog", "Panel 5.B: The second frog", etc. In addition, I would like the individual picture caption (in this case the captions for figure 1, 2, 3 and 4) to be in a normal font instead of a bold font.

• The subcaption package uses \subcaption to do what you want. In also uses a subfigure environment which is basicially a minipage with subcaptions. As for vertical spaces, you can also play with \abovecaptionskip and \belowcaptionskip (lengths). – John Kormylo Apr 29 '18 at 15:30
• Thank you for your comment, Mr. @JohnKormylo. This seems to be in line with what was written by leandriis. – Andreas Apr 29 '18 at 17:40

Regarding your first question, you can use a \vspace of your choice. (In the following example, the contents do not fit onto the page any longer due to the space that I intruduced.)

The second part can easily be achieved by using a package that is dedicated to subfigures. In the following example, I use the subcaption package and simply replaced all occurences of minipage by subfigure. Additionally, I have changed the appearence of the subfigure's captions to match your description:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[margin=2.5cm, showframe]{geometry}
\usepackage{graphicx}
\usepackage{lipsum}
\usepackage[skip=0.33\baselineskip]{caption}
\captionsetup[figure]{
font=bf,
size=normalsize,
justification=centerlast,
}
\usepackage[labelformat=simple]{subcaption}
\captionsetup[subfigure]{
font=normal,
size=normalsize,
justification=centerlast,
}
\renewcommand*{\thesubfigure}{Panel \thefigure\Alph{subfigure}:}

\begin{document}
\newcommand{\figurewidth}{0.95}
\newcommand{\figureheight}{0.375}
\begin{figure}[ht]
\centering
\begin{subfigure}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{example-image}
\caption{The first frog}
\end{subfigure}%
\begin{subfigure}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{example-image}
\caption{The second frog}
\end{subfigure}
\vspace{1cm}

\begin{subfigure}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{example-image}
\caption{The third frog}
\end{subfigure}%
\begin{subfigure}{0.5\textwidth}
\centering
\includegraphics[width=\figurewidth\linewidth, height=\figureheight\textheight]{example-image}
\caption{The fourth frog}
\end{subfigure}
\vspace{2ex}
\caption{A couple of frogs}
\parbox{\linewidth}{\small\lipsum[1]\vspace{2ex}}
\end{figure}
\end{document}


• Perfect, this is exactly what I wanted! Thank you very much, @leandriis. – Andreas Apr 29 '18 at 17:38