1. An image processing apparatus comprising: field separating means for separating an original image into plural types of fields in response to a first image signal obtained at a first density of the original image; characteristic value calculating means for calculating a characteristic value of the original image in response to a second image signal of the original image obtained at a second density which is higher than the first density; discrimination means for discriminating an image field of the original image in accordance with the characteristic value calculated by the characteristic value calculating means to correspond to the type of the field by the field separated by the separating means; and an image processing means for processing a predetermined image processes corresponding to a result of discrimination of the image field performed by the discrimination means, on the second image signal.