[Tex/LaTex] Referencing Subfigure in Subfloat

subcaptionsubfloats

I want to reference a subfigure like so:

\documentclass{article}
\usepackage[demo]{graphicx}
\usepackage{caption}
\usepackage{subcaption}

\begin{document}

\begin{figure}
     \subfloat[A subcaption.]{\label{figure:subfigure1}\includegraphics[width=2cm]{logo}}
     \caption{A caption.}
     \label{figure:figure1}
\end{figure}

\noindent
Subfigure \ref{figure:subfigure1}, Figure \ref{figure:figure1}.

\end{document}

However, I am getting a "Reference undefined" warning and the output is:

enter image description here

When I am using

\usepackage{subfig}

instead of 

\usepackage{caption}
\usepackage{subcaption}

the output is as expected (references are all found).

What am I doing wrong?

Update

I checked the package versions. Indeed, they are old:

Package: subcaption 2008/08/31 v1.0b 
Package: caption 2009/10/09 v3.1k caption kernel (AR)

Best Answer

First of all \subfloat was indeed defined in very early versions of the subcaption package but this was never a documented feature (and has proven to be a very bad idea anyway since it was not 100% compatible with \subfloat offered by the subfig package). As equivalent the subcaption package offers the (well documented) command \subcaptionbox with a slightly different (and enhanced) syntax and behaviour:

\documentclass{article}
\usepackage[demo]{graphicx}
\usepackage{caption}
\usepackage{subcaption}

\begin{document}

\begin{figure}
     \subcaptionbox{A subcaption.\label{figure:subfigure1}}{\includegraphics[width=2cm]{logo}}
     \caption{A caption.}
     \label{figure:figure1}
\end{figure}

\noindent
Subfigure \ref{figure:subfigure1}, Figure \ref{figure:figure1}.

\end{document}

(Please note when using \subcaptionbox the \label needs to be placed inside the caption argument, not inside the content argument.)

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