Photo credits
Every photograph here is credited beside the picture it belongs to. This page gathers them in one place.
Updated
How images are used
Photographs on this site come from two places: images licensed by the publisher, and images published under a Creative Commons licence.
Where a licence requires attribution, the credit appears directly under the photograph as well as in the list below, because that is what those licences ask for. Where no attribution is required, no credit line is shown and the entry below says so.
Illustrations
Diagrams and schematic drawings, such as the vehicle category comparison, are made for this site and are not photographs.
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Every image carries a description of what is visible in it. We describe what the picture shows rather than what we would like it to prove: a caption is a claim, and an empty quay photographed in October says something different from an empty quay in July.