The PENTAX DA * 50-135mm F2.8 ED (IF) telephoto zoom lens is designed for exclusive use with PENTAX digital SLR cameras, delivering the highest level of ultimate optical image quality. With aspherical elements, The tightly sealed, weather-resistant and dust-resistant construction enhances durability for use in both rainy and dusty conditions, making it a perfect companion for the weather-resistant PENTAX DSLR bodies. The SDM focus system incorporated in this lens results in a smoother, quieter autofocusing operation using a built-in supersonic motor.