Unexpected artifacts in a digital photograph

Abstract

This article investigates an unexpected phenomenon observed in a recent digital photograph, in which the logo of a non-sponsoring sports company appears on the jersey of a famous football player in just one of a sequence of images. After eliminating deliberate image tampering as a cause, a hypothetical sequence of circumstances is proposed, concerning the lighting, dominant colours, infrared sensitivity, optical preprocessing, image enhancement and JPEG compression. The hypotheses are tested using a digital SLR camera. The investigation is of interest in a forensic context, firstly as a possible explanation in case such a photograph is observed, and secondly to be able to confirm or refute claims of such artifacts put forward claiming that a hypothetical image is not really what it claims to be.