The facial recognition is very sensitive to the image quality. So, extreme care must be taken when taking images. The restrictions described below, if done properly, may bring the best possible results in the execution of the face verification (1:1) and identification (1:N) operation.
Front pose must be used (full face). Head rotation must be less than ± 5 degrees from the forehead in all directions – up/down, rotated left/right, tilted left/right.
Example of a photo with an unfavorable position:
The expression must be neutral (no smiling) with both eyes opened, and mouth closed. You must try your best to follow this specification. A smile with closed jaw is allowed, but not recommended.
Examples of expressions that are not recommended.
- Smile where the inside of the mouth is exposed (opened jaw);
- Raised eyebrows;
- Closed eyes;
- Eyes not directed towards the camera;
- Forehead or eyebrow frown;
- Hair covering the eyes;
- Glasses frame covering part of the eye.
Beard, mustache, and other changeable features of the face influence the quality of the recognition and if frequent facial changes are common in an individual, make sure that the image being used for the user in the database is updated.
The lightning must be evenly distributed across each side of the face and from top to bottom. There must be no significant direction of light or visible shadows. You must take care to avoid hot spots. They are usually caused when a focused light source of high intensity is used for illumination.
There should be no lighting on the glasses. This can be achieved usually by increasing the angle between the light, the individual and the camera by 45 degrees or more. If the illumination reflections cannot be removed, then the glasses must be taken off. (Although, this is not recommended, since the face recognition usually works better when comparing people wearing glasses with themselves wearing the same glasses). Glasses must have transparent and clear lenses so that the eyes and iris are clearly visible. Glasses heavily colored are not acceptable.