Usando bmargin para eliminar espacios en blanco

Question

yo interpretoestecomo me dice que eso bmargines lo que elimina el espacio en blanco entre la parte inferior del documento y las figuras inferiores. Pero si ejecutas el código verás que el espacio en blanco sigue ahí, ¿qué estoy haciendo mal?

EDITAR: Me acabo de dar cuenta de que la segunda página tenía correctamente bmargin=0. ¿Cómo hago para que esto funcione también en la primera página?

EDIT2 (respuesta al comentario): La razón por la que uso ese particular voffsetes simplemente para que parezca un poco más centrado, idealmente me gustaría controlar exactamente voffsety bmarginen la primera página, parece que puedo hacerlo en todas las demás páginas, pero no el primero.

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[margin=0pt, paperheight=830pt, voffset=60pt, bmargin=0pt]{geometry}
\pagestyle{empty}

\begin{document}

\begin{figure}[h]
    \centering
    \includegraphics[width=0.6\linewidth]{example-image-a}
    \label{fig:my_label}
\end{figure}
\begin{figure}[h]
    \begin{subfigure}{.5\textwidth}
        \centering
        \includegraphics[width=0.7\linewidth]{example-image-a}
        \label{fig:numberthree}
    \end{subfigure}
    \begin{subfigure}{.5\textwidth}
        \centering
        \includegraphics[width=0.7\linewidth]{example-image-b}
        \label{fig:numberfour}
    \end{subfigure}
    \label{fig:pics2}
\end{figure}
\begin{figure}[h]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image-a}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image-b}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}

\end{document}

EDITAR3:Este código es para mi respuesta en el comentario.

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[margin=0pt, paperheight=830pt, voffset=20pt, bmargin=50pt]{geometry}
\pagestyle{empty}

\begin{document}

\begin{figure}[h]
    \centering
    \includegraphics[width=0.5\linewidth]{example-image}
    \label{fig:my_label}
\end{figure}
\begin{figure}[h]
    \begin{subfigure}{.5\textwidth}
        \centering
        \includegraphics[width=0.7\linewidth]{example-image}
        \label{fig:numberthree}
    \end{subfigure}
    \begin{subfigure}{.5\textwidth}
        \centering
        \includegraphics[width=0.7\linewidth]{example-image}
        \label{fig:numberfour}
    \end{subfigure}
    \label{fig:pics2}
\end{figure}
\vspace*{\fill}
\begin{figure}[h]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}
\begin{figure}[h]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}
\begin{figure}[h]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}\begin{figure}[h]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}
\begin{figure}[h]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}

\end{document}

Answer 1

Prueba esto:

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[paperheight=830pt, margin=0pt, noheadfoot]{geometry}
\pagestyle{empty}

\makeatletter
\@fptop=0pt% distance from top of text area to first [p] figure
\@fpbot=0pt% distance from bottom of text area to last [p] figure.
\makeatother

\begin{document}
\begin{figure}[p]
    \centering
    \includegraphics[width=0.6\linewidth]{example-image-a}
    \label{fig:my_label}
\end{figure}
\begin{figure}[p]
    \begin{subfigure}{.5\textwidth}
        \centering
        \includegraphics[width=0.7\linewidth]{example-image-a}
        \label{fig:numberthree}
    \end{subfigure}
    \begin{subfigure}{.5\textwidth}
        \centering
        \includegraphics[width=0.7\linewidth]{example-image-b}
        \label{fig:numberfour}
    \end{subfigure}
    \label{fig:pics2}
\end{figure}
\begin{figure}[p]
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image-a}
    \label{fig:numberthree}
\end{subfigure}
\begin{subfigure}{.5\textwidth}
    \centering
    \includegraphics[width=0.7\linewidth]{example-image-b}
    \label{fig:numberfour}
\end{subfigure}
\label{fig:pics2}
\end{figure}
\end{document}