Follow the guidelines below to improve the face recognition capabilities of iPhoto '09 and iPhoto '11.
Note: Only faces that have been automatically detected in your photo library will help iPhoto match faces. Manually identified faces will not aid iPhoto's face-matching ability. See Faces not detecting all images of a person in your library for more information.
Identifying profiled faces
Matching a name to a profiled face, as in the image below, may help iPhoto find and suggest more profile shots of that person in that person's face tile in Faces. Manually matching a profile image of a face in your library will not help with direct shots of that person. Identify and confirm direct and profile shots in order for iPhoto to suggest both variations.
Identifying a face at different stages of age
If you happen to have photos of the same person spanning a long time frame, such as photos from baby through adult years, identifying all of them under the same name may help iPhoto in finding more matches of that particular person.
Identifying back-of-the-head images
iPhoto should not detect the back of a person's head when matching faces. If the back of a person's head is automatically detected, it would be better to eliminate the detected "face" in order to maintain iPhoto's ability to recognize this person.
Select the photo with the detected back-of-head and select the Name icon in the tool bar. Hover over the "unknown face" and then select the X that appears on the top left of the face box.
Note: If you have manually added a missing face to be the back of someone's head, this will neither positively nor negatively affect iPhoto's ability to recognize that person in other photos.
Identifying blurry, badly lit or very small faces
If iPhoto has automatically detected a face from an image that is blurry, badly lit, or has a small face, then identifying it with a name will broaden the suggested photos for that particular person in that person's face tile in Faces.
Note: In these types of photos, faces are harder to distinguish and iPhoto may incorrectly suggest these types of faces in other face tiles as well.