Pentax 17-70mm f/4 DA SMC AL IF SDM Lens for Pentax Digital SLR Cameras Extra Zoom For A Wide Range Of Shooting Applications From Wide Angle To Telephoto Focal Length Equivalent To 26mm - 107mm Exclusive Lens Sdm Autofocus For Pentax(r) Digital SLR Bodies With Sdm Capabilities Super-protective Coating Protects Exposed Lens Elements Quick-shift Focus System Allows Instant Switching From Auto Focus To Manual Focus Equivalent focal length of 26-107mm in 35mm format, when used with digital SLR cameras. ED and aspherical elements compensate for chromatic and spherical aberration. The image circle of the lens has been created to match the smaller image recording area of digital SLR cameras. The Quick-Shift Focus System allows to instantly shift to manual focus once the subject is captured by AF.