The nature of photographic resolving power is discussed and attention called to the widespread misconception of it that exists at the present time. Most of the detailed discussion applies specifically to photographic objectives intended for use in aerial photography but the general approach to their photographic resolving power is applicable to studies of the photographic performance of all types of optical systems. An annulus type of target is proposed as more suitable than line targets. A method is given for the selection of the photographic focal plane when the essential requirement of the photographic use is the acquisition of maximum information. General remarks are made on the proper trend to be followed in the future design of photographic objectives. Results are presented on a study of a number of well known types of photographic objectives used for aerial photography.