digiKam supports an impressive range of file formats, so you can use the application to handle RAW files, movies and everything in between. But what if you want to explicitly exclude a specific type of files? digiKam offers a simple solution for that.
Choose Settings → Configure digiKam and switch to the MIME Types section. To exclude, for example, the PPM format, enter -ppm in the Image Files field. You can add multiple formats using a space as separator. Excluding specific formats from digiKam doesn’t actually delete them, but simply hides them from digiKam and removes all metadata from the digiKam databases. So be careful when using exclusion filters if you don’t want to lose tags, ratings, and other metadata.
Tech writer covering Linux and open source software
Scribbles and Snaps 
That could be useful, but is it possible to ignore certain directories (like .rawstudio)?
/Simon
I agree with Simon!
See:
https://bugs.kde.org/show_bug.cgi?id=217709
You call this … simple ?!!!
It would have been better to display the list of mimetypes manages by digikam and allow users to unselect. You could even have some profiles ( Images only, Image & video, professional photography )