To make sure photos that contain faces are properly detected if they were imported with iPhoto 09 8.1, first install then 8.1.1 update, and then do this:
- Select the imported photos that include faces. I found that the Photos view made it easier for me to find and select the photos I wanted to include.
- Ctrl-click or Right-click one of the photos, and select Detect Missing Faces from the contextual menu.
iPhoto’s Detect Missing Faces option
iPhoto will examine the selected photos for faces that might not have been identified, or were misidentified and do its best to correct the errors.
The Faces feature still isn’t perfect, but iPhoto does seem to be better at finding photos with faces now that the 8.1.1 update is out.