Those who doubt that  reconnaissance aerial photography was taken from as low as 25 feet should look at the images in Evidence in Camers, Special Edition on Photographic Reconnaissance and Photographic Intelligence published by the(UK) Air Ministry, March 1945 (Reprinted by the GeoInformation Group, 2003).

For example the photograph on page 8 of a radar antenna  in Denmark 

Jim Caruth

Lead Curator, Modern Mapping

The British Library