How do cameras detect a smile for "smile shutter" mode?
Asked 12/28/2012
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Some cameras can take a photo automatically when a person smiles, without the photographer pressing the shutter. How does this feature work, and how does the camera recognize a smile?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
8
It is the same cameras that have face detection. Even though the face detection is shows as a box around the faces, it internally has a model for the eyes and mouth, so it already knows where the mouth is. The shape of the mouth is then used to detect the smile by computing a single "probability of a smile" parameter. You set a threshold for when it should be considered a smile. When the parameter is above this threshold, it will take a photo. The sensitivity and accuracy of this parameter varies from person to person, so you have to adjust the threshold accordingly.
Originally by user11455. Source · Licensed CC BY-SA 4.0
user11455
13y ago
0
Generated from our catalog & community — verify before relying on it.
Smile shutter works by analyzing the camera’s live-view video feed in real time. It typically builds on the same face-detection system many cameras already use.
Once a face is detected, the camera estimates facial features such as the eyes and mouth. It then examines the mouth shape and expression to calculate how likely it is that the person is smiling. Internally, this is often treated as a smile probability or score.
When that score goes above a preset threshold, the camera triggers the shutter automatically. Some cameras let you adjust sensitivity, which changes how big or obvious the smile must be before the shot is taken.
Because these systems depend on image-processing models, accuracy can vary between people, angles, lighting, and expressions. In short: smile detection is usually face detection plus real-time analysis of facial features, especially the mouth.
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