The Canon EF 75-300mm f/4-5.6 III is an affordable, lightweight telephoto zoom lens for Canon DSLR cameras. Its key specification is a 75-300mm focal range with a variable maximum aperture of f/4 at 75mm, narrowing to f/5.6 at 300mm. The lens construction uses 13 elements in 9 groups and has a minimum focusing distance of 1.5 meters (4.9 ft).

It uses a 58mm filter thread, weighs 480 grams (16.9 oz), and has physical dimensions of 71mm in diameter by 122mm in length. It features a micro-motor autofocus system, which is not particularly fast or quiet, and the front of the lens rotates and extends during focusing. A critical point is that this lens does not have Image Stabilization (IS).

Important Performance Context:This lens is known for being one of Canon's most budget-friendly telephoto options. However, it has a reputation for relatively soft image quality, especially at its 300mm maximum focal length, and can exhibit chromatic aberration (color fringing). The combination of a slow, variable aperture and the lack of image stabilization means it performs best in bright daylight conditions where fast shutter speeds can be used to minimize camera shake. For owners of APS-C sensor Canon cameras (like the Rebel series), the effective focal length becomes approximately 120-480mm, offering significant reach. While it provides an inexpensive entry into telephoto photography, its optical limitations are significant, and most users are better served by alternatives like the Canon EF-S 55-250mm IS STM for crop-sensor cameras.