How the dark circle check works
After finding the face, the tool places 68 landmark points and uses the six around each eye to locate the eye openings. It then samples a region just below each eye and measures its brightness pixel by pixel, skipping pixels that are almost pure black or white because those are usually shadows or reflections. The darker that region reads, the higher the score.
The score is grouped into five bands: Minimal, Mild, Moderate, Significant and Severe. The overlay shows which pixels were sampled, so you can check that the tool looked at your under-eye area rather than a lash line or the frame of your glasses.
Lighting decides most of the result
Because the check works from brightness, the light in the photo matters more than anything else. Overhead light casts the brow's shadow straight into the under-eye area and makes almost anyone look tired. Side light darkens one eye more than the other. Soft daylight from in front of you, with no strong lamp above, gives the most honest reading.
Skin tone matters too. The measure is brightness, and natural pigmentation around the eyes differs between people, so the score is most useful for comparing your own photos under the same conditions, not for comparing different people.
- Face a window; avoid overhead ceiling lights.
- Remove concealer and tinted eye cream for a fair comparison.
- Keep the camera at eye level so the brow does not shade the eyes.
- Glasses frames and lenses can cast shadows or reflections in the sampled area.
- Use the same place, time of day and distance when comparing photos.
What it cannot tell you
Under-eye darkness has many causes: genetics, thin skin, pigmentation, hollows that cast shadows, allergies, rubbing the eyes, dehydration and sleep. The tool sees only that a patch of pixels is darker than expected; it cannot tell which cause applies, and a high score is not a diagnosis. If darkness or swelling around the eyes appears suddenly, is on one side only or comes with other symptoms, talk to a doctor or pharmacist rather than relying on a photo tool.