Context:
I'm currently including quite an amount of pictures into my beginner's guide. In case of , a valid image is used I created several copies in different file formats, such as PNG, EPS and PDF.
Edit: I use pdflatex to create my documents.
Edit2: Latest research found this answer to above question, which is similar to a certain degree. Hence I flag this question [duplicate].
Question in addition to above:
How does LaTeX prioritize images for inclusion?
pdftex.def. The default will be overwritten when using\DeclareGraphicsExtension. – Johannes_B Mar 20 '16 at 12:24