This lens replaces the previous high quality L-series 28-70mm f/2.8 lens, with a lens of even greater caliber. The range has been extended to cover an ultra-wide angle of 24mm, which makes it ideal for digital as well as film shooters, and the optics are even better than before with two Aspherical elements and a totally new UD glass element. It's now sealed and gasketed against dust and moisture, and a new processing unit makes the AF faster than ever.
Two Aspherical Elements
A lens design incorporating elements ground so the curve of the surface does not describe an arc of a circle. Especially useful in reducing distortion in wide angle lenses.
UD Element
UD glass is one of the new technologies to open new possibilities to develop the zoom lenses with low weight and high optical performance. UD elements make it possible to correct chromatic aberrations whilst maintaining low weight.