I really like the view in the Faces section of iPhoto when you are identifying possible matches. You get the closeup of just the picture and you can see all of the ways the person has changed over the years (assumine you are actually looking at a match).
I would like to automate the process of generating a slideshow that shows only the person's face. Does anyone know of how it might get done in iPhoto or with a third-party product that could leverage iPhoto's faces data?
First: You can't do it with iPhoto, it's just not a feature.
Next: Those faces thumbnails are stored inside the iPhoto Library package - in the Data folder on some versions, the Thumbnails folder on later ones.
If you make an alias to that folder you could possibly access them that way using another app. However, they are scattered hither and yon throughout the folder, in multiple subfolders and may well be difficult to find. That said they include they all include _face0 in the filename so a Smart Folder will help find them
But... However, these are very small (200 - 300 pixel on the longest side) images and it's unlikely that they will perform well in a slideshow.
I haven't used iPhoto in a long time, since I'm using Aperture now; but there, you can just open a person's pictures, and just start a slideshow.
Since Aperture (and I think iPhoto too) always uses the currently shown set of photos for a slideshow, these pictures will be shown in the slideshow.
Alternatively, you can create a smart album with one condition: Face is [person's name]; you can then make slideshow of it.
