Want to quickly find pictures of yourself, your friends, and your family members within your Photos for OS X library? Check out the Faces album.
Face detection is nothing new when it comes to digital photography: Facebook, iPhoto, and countless other programs and websites have offered it in years past. Photos for OS X carries on that proud tradition with an updated version of Faces in the app.
When you first launch Faces, it automatically detects and finds faces from your photographs for you to tag, then lines them up along the bottom of the screen under the Suggested Faces category. If Faces has recognized a face you don't want to tag (or an object that happens to look like a face), just select it and press the delete key to remove the tag.
When you double-click on a Suggested Face, you're prompted to enter in the name of the person in question. Photos pulls from your Contacts to auto-fill names, though you can also create Faces profiles that have no contact card associated. When you've found the person in question or typed in the name you want, click on that selection.
Photos will then try to find other unmatched faces that look similar to your new Faces profile; they're auto-selected as correct by default, though you can click any wrong face identifications to remove it. When you're finished, press Add and Continue.
Afterwards, Faces will let you know how many other pictures of the person it was able to find. Faces's recognition is on par for standard facial expressions, but you may have to go through this process several times if you have photos of the person making strange faces, wearing glasses, and the like.
Once you're finished identifying people, you'll have a series of Faces profiles in bubble form above the Suggested Faces drop-down. Double-click a face to see all the images that Photos has found of that person.
Each individual Faces profile can be viewed as full photos or face bubbles; if Photos thinks it has additional photos of this person, you'll also see the "[Person] may be in additional photos" message in the top right corner along with an Add button. You can exit an individual Faces profile by pressing the back button at any time.
Should you want to remove a Face from a photo, just navigate to the photo and click the info button, then select the face under the Keywords section and delete it.
If you want to remove a whole Faces profile, select one of the Faces bubbles and press delete.