1. An information retrieval apparatus comprising: an obtaining unit configured to obtain dynamic ranges or re-quantization codes of a target object to be retrieved and dynamic ranges or re-quantization codes of each of comparison objects to be compared with the target object, the dynamic ranges or re-quantization codes of the target object and the dynamic ranges or re-quantization codes of the comparison objects being obtained as a result of adaptive dynamic range coding; a distance computation unit configured to compute distances between the target object and the comparison objects using the obtained dynamic ranges or re-quantization codes of the target object and the obtained dynamic ranges or re-quantization codes of the comparison objects; and a comparison unit configured to compare the distances between the target object and the comparison objects to select one of the comparison objects having a minimum distance.