[Tex/LaTex] How to let background image cover entire Beamer slide

backgroundsbeamer

I successfully use the usebackgroundtemplate command to set a background image for a specific slide in Beamer as follows

enter image description here

\documentclass{beamer}
\mode<presentation> {
\usetheme{CambridgeUS}
}

\begin{document}

\usebackgroundtemplate{%
  \includegraphics[width=\paperwidth,height=\paperheight]{example-image-a}} 

\begin{frame}[t]
\frametitle{hello}
blahblah
\end{frame}

\end{document} 

However, the image seems to have just covered the main body area, the background of the \frametitle is still white as before. How could I set this image as background for the entire slide? Or at least for the \frametitle as well (just for the slides I want, not for the entire presentation)? Or any better solutions?

Best Answer

The background colour for the frame title in the CambridgeUS theme uses the beaver colour scheme and is set to

\setbeamercolor{frametitle}{bg=gray!10!white}

You can remove the entire background colour by adding

\setbeamercolor{frametitle}{bg={}}

after loading the theme:

enter image description here