[mkenny]

Thanks for the pointers. I am fairly well up on the theory of Air Photography but in the 1940's there was no standard tests for resolution. Today an ordinary camera will give you a resolution of 100 lines /mm rather than the 10-20 lines/mm that passed for acceptable in 1940 air views.
I think there was no real quality difference between the Allied or German photographs but would have liked to have seen it with my own eyes. Rather than getting bogged down in a complicated debate with reams of technical specifications I prefer the simple method of looking at the real thing. It appears that 3-9 foot was the smallest discernable object for F36/30,000 ft. combination and the German Rb 75/30 was not that much better.