As a rule, any file that has a defined pixel size will allow 100% zoom (1 to 1 pixel mapping on screen) using the original file.
This is true for most image file formats. It is also worth noting that using this feature has significant performance impact for the FotoWeb server. This is also the case for RAW files.
Fotoware also supports zooming into PDF and other document types for which a preview has been successfully generated. This is true, for instance, for Word and PowerPoint documents and PDF's.