[OS X TeX] Latex from command line vs. Texshop

[Curiouslearn]

Hi All,

I have written a quiz in latex that has some .png figures in it (using
the \includegraphics[scale=0.5]{moviebooks.png} command).

When I compile the file from my TexShop, it creates a PDF without
errors but some warnings. However, if I compile it from the command
line using

latex Quiz2.tex

I get the following error. I will post a minimal example if necessary.
But possibly someone may know why this might happen. Any suggestions?

                           ! LaTeX Error: Cannot determine size of
graphic in moviebooks.png (no BoundingBox).

Thanks very much for your help.