Radiographs pick up caries by showing radiolucent areas where mineral loss has occurred, but that contrast only appears once a lesion has progressed enough. In the early stages of proximal caries, demineralization often starts in enamel and may not create a visible radiolucent zone yet, so the lesion can be radiographically invisible. Bitewing images help by capturing the proximal surfaces across the contacts, but even these can miss early lesions due to subtle mineral loss, the thickness of enamel, and projection/overlap limitations. That’s why radiographs are useful for detecting caries that have advanced or are near restorations, but they’re not reliable for spotting very early proximal lesions on their own; clinical examination and other diagnostic tools are still important for early detection.