Paul Smith wrote:
Is it really necessary to declare in the preamble
\usepackage{lmodern}
when the latin modern fonts are already installed?
Yes, because you can have installed many fonts and LaTeX needs to know which fonts it should use for your document.
For instance, I
have tetex-cmsuper installed and I get nice looking pdf documents
without declaring \usepackage{lmodern}.
Possibly cmsuper is set as default font when it is installed. But this depends on your LaTeX distribution.
regards Uwe
