There are some requirements to face images FaceSDK can work with. The photo must be taken full-faced and oriented vertically. It must contain the whole face of the person you need, including the head. The face on the photo must not be covered with hands or glasses and it is not recommended that the mouth be open too much. Besides, the photo must be taken in good lighting conditions. For FaceSDK to recognize a face correctly, please make sure that your face images are as close to these requirements as possible.