Canon's budget EF telephoto with USM motor — marginally improved over the Mark II but still basic optics.
The Canon EF 75-300mm f/4-5.6 III USM launched in 1999 as a minor update to the Mark II, adding USM autofocus motor for quieter operation. Like its predecessor, it was one of Canon's cheapest telephoto options, often bundled with entry-level EOS bodies.
Optical quality remains poor — soft at 300mm even stopped down with noticeable chromatic aberration and low contrast. The USM motor is the micro-USM type, quieter than the DC motor in the non-USM III but still without full-time manual focus override.
Canon EF mount with 58mm filter thread. Weighs approximately 480g. Full-frame coverage. No image stabilisation. No weather sealing. Minimum focus distance 150cm. Virtually identical optically to the Mark II — the USM motor is the only meaningful change.
Extremely common used — typically under £30. The non-USM Mark III is even cheaper. Both are outperformed by the EF 70-300mm f/4-5.6 IS USM in every optical measure. Only worth buying as an absolute budget telephoto for casual outdoor use.