What makes up the smile score
The happiness figure comes from the same expression network the Emotion analysis uses: it is how strongly the face matches the happy expression it learned from labelled photos. The other figures come from landmark geometry. Mouth curve measures how far the corners of the mouth lift relative to the centre of the lips. Teeth visibility looks at how far the lips part. Eye squint compares how open the eyes are, because the muscles of a full smile push the cheeks up and narrow the eyes.
The natural smile score leans on that last signal. Smiles that lift the mouth without narrowing the eyes are often described as polite or posed smiles, while smiles that crinkle the eyes are often described as genuine. The tool reports this as a pattern in the photo, not as a judgement of how anyone feels.
Getting a clear smile reading
- Keep the head level: tilting it changes where the mouth corners sit relative to the lips.
- Avoid hands, hair or a phone near the mouth.
- Use soft front light so shadows do not hide the mouth corners.
- A closed-lip smile scores low on teeth visibility by design; that is not a flaw.
- Sunglasses hide the eyes, so the natural smile score is unreliable with them on.
Using it to pick your best photo
The most practical use is choosing between several shots taken a few seconds apart. Run each through the analysis and look at the breakdown rather than the headline. A photo with a high mouth curve but almost no eye squint often looks posed in a profile picture; one with balanced curve and squint usually reads as relaxed. If two shots score about the same, the scores have done their job and the choice is yours.
Photographers have long asked people to think of something funny instead of saying a word, because a laugh moves the cheeks and eyes as well as the mouth. You can try the same trick here: take a few frames with the camera, compare the natural smile scores, and see whether the advice holds for your face.
Limits
The scores describe one frame. A smile captured mid-movement can score lower than the same smile a fraction of a second later. People with facial differences, braces, facial paralysis or simply a different resting face can get readings that say nothing about their happiness. As with every analysis on this tool, use it for fun and for comparing your own photos, not for assessing other people.