1. A method for providing a notification on a face recognition environment, comprising: (a) obtaining an input image that is input in a preview state; (b) comparing feature information for a face included in the input image with feature information for a plurality of reference images of people stored in a predetermined database to determine, in real-time, whether the input image satisfies a predetermined effective condition for photographing, the predetermined effective condition for photographing being information regarding a condition necessary for recognizing the face included in the input image at a higher accuracy level than a predetermined accuracy level; and (c) providing a user with a predetermined feedback for photographing guidance that corresponds to whether the predetermined effective condition for photographing is satisfied.