При попытке на систму, в которой нет КДЕ3 сделать
sudo apt-get install kde4-digikam
имеем

Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
  digikam digikam-data digikam-i18n kde-settings kde4-digikam-data kde4-digikam-i18n kdeaddons-konqueror kdebase-konqueror kdebase-libkonq
  kdelibs libavahi-qt3 libdigikam libkdcraw libkdcraw4 libkdcraw4-common libkde4-digikam libkexiv2 libkexiv24 libkipi
The following NEW packages will be installed:
  kde4-digikam kde4-digikam-data kde4-digikam-i18n kdeaddons-konqueror kdebase-konqueror
   libkdcraw libkdcraw4 libkdcraw4-common libkde4-digikam libkexiv2 libkexiv24 libkipi
0 upgraded, 20 newly installed, 0 removed and 0 not upgraded.
Need to get 0B/30.5MB of archives.
After unpacking 85.8MB of additional disk space will be used.


Т.е. дополнительно по зависимостям тянутся
digikam 
digikam-data 
digikam-i18n 
kde-settings 
kdeaddons-konqueror 
kdebase-konqueror 
kdebase-libkonq 
kdelibs 
libavahi-qt3 
libdigikam
которые, скорее всего, не нужны.