1. An image processing apparatus comprising: an extraction unit that extracts a feature from image data; a memory that stores personal feature information including short term feature information to which a validity period of time is set and long term feature information to which a validity period of time is not set; a matching unit that compares the feature extracted by said extraction unit with the personal feature information stored in said memory to obtain a comparison result used to recognize a person having the extracted feature; and a control unit that sets a feature registration mode for updating the personal feature information stored in said memory by registering at least one of new short term feature information or new long term feature information, wherein, in a case where the feature registration mode is not set, said matching unit compares the feature extracted by said extraction unit with the long term feature information and the short term feature information within the set validity period of time and uses the comparison result to recognize the person having the extracted feature, and wherein, in a case where the feature registration mode is set, said matching unit compares the feature extracted by said extraction unit only with the long term feature information and uses the comparison result to recognize the person having the extracted feature even if the short term feature information within the set validity period of time exists.