A closer view of the film defect in the picture taken at Doetinchem. Clearly visible is the flesh-like aspect of the dark area of the artefact. Twigs are visible in the foreground, implying that the undesired substance was already a part of the film before it was exposed. On places where a twig appears in front of a dark area in the blister, the twig takes on a darker colour. This is not the case in other parts of the picture where twigs partially run across dark areas. Together with the contrast-rich appearance of the blister, this proofs that we are not dealing with a distant object that is part of the scenery, but with a localised defect of the film emulsion.
[Photo by W. VAN ARK - thanks to Frits VAN DER VELDT for submitting us this picture]