SIGCHI Latex Format display subfigures

\usepackage{graphics} % for EPS, load graphicx instead
\usepackage[caption=false]{subfig}

\begin{figure}
\centering
\subfloat[Blur]{\includegraphics[width=0.45\columnwidth]{figures/interface_blur.pdf}}
~
\subfloat[Distortion]{\includegraphics[width=0.45\columnwidth]{figures/interface_distort.pdf}}
\\
\subfloat[Mosaic]{\includegraphics[width=0.45\columnwidth]{figures/interface_mosaic_line.pdf}}
~
\subfloat[Rotation]{\includegraphics[width=0.45\columnwidth]{figures/interface_rotate.pdf}}
\caption{Potential for 0.5 V bias.}
\label{fig:EcUND}
\end{figure}