The arithmetic of cropped sensors and telephoto glass is one of the more useful free lunches in photography. The Canon R7 — a serious APS-C body with genuinely professional-grade autofocus and a 32.5-megapixel sensor — transforms the EF 70-200mm f/4L into a 112–320mm equivalent. A zoom range that, on full frame, would require an expensive, heavier f/2.8 lens or a dedicated super-telephoto prime. Here it arrives via a quarter-century-old zoom that trades used for well under $600.