I generally don’t use iPhoto a lot on my system. I have a several thousand photos; they are well organized with tags and smart groups. I really only use iPhoto to import my new pictures.
Something that frustrates the hell out when I do occasionally use iPhoto is the Faces detection that brings my iPhoto (and sometime my system) to a crawl.
The following steps will disable iPhoto’s Faces detection!
1. Quit iPhoto
2. Open the Terminal Application (Applications/Utilities/Terminal.app)
3. Type the following (exactly as is):
defaults write com.apple.iPhoto PKFaceDetectionEnabled 0
(then return)
4. Type the following (exactly as is):
exit
(then return)
5. Quit Terminal
6. Start iPhoto
If you wish to re-enable Faces Detection then simply change the the 0 to a 1 from step 3 as shown below.
defaults write com.apple.iPhoto PKFaceDetectionEnabled 1