Face recognition is very sensitive to image quality so maximum care should be attributed to image acquisition.
Pose
The frontal pose (full-face) must be used. Rotation of the head must be less than ±5 degrees from frontal in every direction – nodded up/down, rotated left/right, tilted right/left.
GM factory replica watchesExpression
The expression should be neutral (non-smiling) with both eyes open, and mouth closed. Every effort should be made to have supplied images comply with this specification. A smile with closed jaw is allowed but not recommended.
Examples of Non-Recommended Expressions
• A smile where the inside of the mouth is exposed (jaw open).
• Raised eyebrows.
• Closed eyes.
• Eyes looking away from the camera.
• Squinting.
• Frowning.
• Hair covering eyes.
• Rim of glasses covering part of the eye.
Face changes
Beard, moustache and other changeable face features influence face recognition quality and if frequent face changes are typical for some individual, face database should contain e.g. face with beard and cleanly shaved face enrolled with identical ID.
Lighting
Lighting must be equally distributed on each side of the face and from top to bottom. There should be no significant direction of the light or visible shadows. Care must be taken to avoid “hot spots”. These artifacts are typically caused when one, high intensity, focused light source is used for illumination.
Eyeglasses
There should be no lighting artifacts on eyeglasses. This can typically be achieved by increasing the angle between the lighting, subject and camera to 45 degrees or more. If lighting reflections cannot be removed, then the glasses themselves should be removed. (However this is not recommended as face recognition typically works best when matching people with eyeglasses against themselves wearing the same eyeglasses). Glasses have to be of clear glass and transparent so the eyes and irises are clearly visible. Heavily tinted glasses are not acceptable.
Web cameras
As web cameras are becoming one of the most common personal video capturing devices, we have conducted small video image quality check. Most of cheap devices tend to provide 320×240 images of low quality, insufficient for biometrical use, however few of higher quality devices deserve a mention: Logitech Quick Cam Pro 4000, Logitech Quick Cam Zoom, and Creative Pro Ex. As a general rule, true 640×480 resolution (without interpolation) and a known brand name are recommended. Images should be enrolled and matched using the same camera, as devices have different optical distortions that can influence face recognition performance.