\documentclass{minimal}
\usepackage{graphicx}
\begin{document}
File with extension given, no conversion:

Lorem ipsum. \includegraphics{{sample.1}.eps}

File in subdirectory, no conversion:

Lorem ipsum. \includegraphics{subdir/{sample-in-subdir.1}.eps}

Explicitly giving the extension, no conversion:

Lorem ipsum. \includegraphics[ext=.eps,scale=.3]{{{sample.1}}}
\includegraphics[ext=.eps,scale=.3]{sample}
\includegraphics[ext=.eps,scale=.3]{{{sample}}}

Letting TeX derive the extension, no conversion:

Lorem ipsum. \includegraphics{{{sample.1}}}

File with extension given, forcing rubber to do a conversion

Lorem ipsum. \includegraphics{{empty1.0}.eps}

Forcing rubber to do a conversion and to find the correct extension

Lorem ipsum. \includegraphics{{{empty1.0}}}
\end{document}
