1. A method for providing a notification on a face recognition environment, comprising: obtaining an input image that is input in a preview state; 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 each of a plurality of predetermined effective conditions for photographing, the plurality of predetermined effective conditions for photographing including a lighting condition, a face size condition or a face direction, wherein the lighting condition is satisfied if a first reference ratio is lower than or equal to a predetermined threshold ratio, the first reference ratio being calculated using a histogram for a region of the face in the input image; determining whether a second reference ratio is lower than or equal to a predetermined threshold ratio if the lighting condition is not satisfied, the second reference ratio being calculated using a histogram for a region located outside the region of the face in the input image; and providing a user with a predetermined feedback for photographing guidance that corresponds to whether the predetermined effective condition for photographing is satisfied, wherein if the second reference ratio is lower than or equal to the threshold ratio, the feedback for photographing guidance including information that an amount of light is sufficient.