As a general 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.
File formats that don't have a real pixel size, but where a preview can still be generated (such as documents and presentations), FotoWeb lets users zoom in on the preview file, which is usually 1200 pixels.
Videos, as well as file formats for which no preview can be created, do not support zooming.