Wide Angle Prime Lenses for the Micro Four Thirds Standard whose focal length is in the 7mm to 18mm range. The size of the sensor on the Micro Four Thirds cameras is half the size of 35mm film therefore the crop factor is 2x, meaning that a 12mm Micro Four Thirds lens will be equivalent (in 35mm terms) to a 24mm lens. The short distance from sensor to the back of the lens combined with the size of the sensor allow these lenses to often be extremely compact for their quality and range. A Prime lens is a lens that only has one focal length, You cannot zoom in or out with these lenses. They are often very high quality lenses as they are designed particularily for that one focal length.