"Being smaller and lighter while maintaining a constant maximum aperture of f/4 across its focal length makes this a very nifty lens for those who requires wide-angle to mid-telephoto coverage. Being the first full-frame L lens to be powered by the Nano USM, RF24-105mm f/4L IS USM provides responsive smooth focusing—suitable for video recording. With its image stabilisation of up to 5-stops, you can achieve sharp images shooting handheld. RF24-105mm f/4L IS USM features an additional control ring on the barrel that could be customised to control exposure settings; shutter speed, aperture, ISO and exposure compensation, effectively providing better control especially while shooting through the Electronic View Finder. The control ring has a tactile, easily distinguished surface and features a clicking mechanism that provides tangible feedback during adjustment. Filter Size: 77mm Max aperture: f/4 Additional Control Ring With Nano USM Dust and Drip Resistant "