This new lens does what many pros thought couldn't be done -
replace the previous L-series 28-70 f2.8 lens with something even
better. Extended coverage to an ultra-wide-angle 24mm 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 sealed and gasketed against dust and
moisture, and a new processing unit makes the AF faster than ever.