Overview
A measurement study, explicitly not a new detector: five pre-registered experiments (E1-E5) mapped to four hypotheses test which explainable feature set (pixel-pattern, frequency-spectrum, or combined) best separates real photographs from AI-generated images. The pipeline specification was locked at v1.0 (stages 0-10) before results ran, with a deliberate negative-control experiment for mismatch shortcuts, JPEG quality levels 90/75/50, and an unseen-generator holdout, culminating in the headline E5 condition (unseen generator + JPEG 75). The repo carries the final results, a separate limitations report, a 20-paper curated reference set with BibTeX, and a CITATION.cff, alongside a written scope statement of what the study is not.