Introduction Before last year’s introduction of the Canon EF200-400mm f4L IS USM x1.4 Extender this model was the only telephoto zoom in the range with a focal length over 300mm. Introduced in 1998 this L-series lens was made to a high specification that still stands today. As well as a two-stop image stabilizer the EF100-400mm f4.5-5.6L IS USM has a fast, quiet ultrasonic AF motor. Like all Canon L-series lenses, it’s made to a high standard but it doesn’t feature environmental sealing – though just how effective that is in zoom is It also has a