The Pentax SMC DA* 50-135mm f2.8 ED (IF) SDM is a professional-grade telephoto zoom lens designed exclusively for Pentax digital SLR cameras with APS-C sensors. Featuring a constant f/2.8 maximum aperture throughout its entire focal range, this lens excels in portrait and medium telephoto work, offering an effective 77-207mm equivalent reach. The optical design incorporates extra-low dispersion glass elements and aspherical components to deliver exceptional sharpness and edge-to-edge clarity whilst minimising chromatic aberration and distortion. The SDM ultrasonic autofocus motor provides quick, near-silent focusing performance, whilst the Quick-Shift Focus System allows instantaneous switching between autofocus and manual focus. Weather-sealed construction and a fixed barrel design make this a versatile workhorse for sports, events, portraiture, and outdoor photography.