The Canon Extender EF 1.4x III is a teleconverter for the Canon EF autofocus mount, multiplying the focal length of compatible EF telephoto and super-telephoto lenses by 1.4x at the cost of one stop of light. It is the third-generation version of Canon's 1.4x EF extender, designed to pair with white-series L telephotos and maintain autofocus and electronic communication with the host body.

At recent UK auction, hammer prices for the Extender EF 1.4x III have sat in a tight £125–£138 band, with a median around £132 across the limited sample available in 2026. These are wholesale saleroom results rather than dealer retail, so what a clean copy sells for at auction today typically lands below what the same unit is worth on the used dealer shelf; condition of the rear protruding element and contact pins is the main swing factor on value and price.