Canon's first stabilised 70-300mm telephoto zoom, better than the 75-300mm but still budget.
The Canon EF 70-300mm f/4-5.6 IS USM was introduced in 2005 as a mid-range consumer telephoto zoom with Canon's Image Stabiliser, providing a lower-cost alternative to the professional 70-200mm f/2.8L and 70-300mm f/4-5.6L IS USM. It was succeeded by the IS II USM (2016) with improved optics, a faster Nano USM motor, and revised IS. On APS-C bodies the 112-480mm equivalent extends reach considerably for wildlife and outdoor telephoto use.
The optical design uses 15 elements in 10 groups. The 58mm filter thread is less common than the 77mm professional standard but shared with the EF 50mm f/1.4 USM and other mid-range Canon EF lenses. At approximately 630g the lens is substantial for a consumer telephoto. Minimum focus distance of 1.5m suits the telephoto use case. IS provides approximately 2 stops of compensation — the original IS algorithm, lower than later Canon IS generations. The Micro-USM (circular USM) motor is faster than a DC motor but slower and noisier than Canon's ring-type USM. Full-time manual focus override is available.
For outdoor telephoto use the 70-300mm IS USM covers wildlife, birds, outdoor sports, and travel subjects across the full range. IS at 2 stops is useful for static subjects; the improvement over a non-IS telephoto is meaningful in adequate light but less effective than later Canon IS generations. Optical quality is good to approximately 200mm; at 300mm wide open some softening is present, typical for this price tier. The Micro-USM AF is reliable for most non-professional stills applications.
On the used market the original 70-300mm IS USM is very affordable. The IS II USM (2016) provides Nano USM, improved IS, and better optical performance at a modest premium — the recommended upgrade for most buyers. Condition checks: IS engagement, Micro-USM AF response at both ends of the zoom range, and zoom ring for smoothness. Compatible with all Canon EOS DSLRs and via EF-RF adapter on EOS R-mount bodies. The 58mm filter thread is shared with several mid-range Canon EF lenses.