For standard to medium long-range applications, offering the utmost level of sharpness, contrast and overall picture clarity. 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.