nikon and pentax both chose to extend their existing lens mounts with autofocus capability, retaining the ability to use older manual-focus lenses with an autofocus body, and driving the lens focus mechanism with a motor inside the camera. later, nikon added silent wave motor (swm) mechanisms into its lenses, supporting both focusing schemes until the introductions of the entry-level nikon d40 and nikon d40x in 2006. pentax introduced its supersonic drive motor (sdm) in 2006 with pentax k10d model and two lenses (da*16-50/2.8 al ed [if] sdm and da*50-135/2.8 ed [if] sdm). since then all pentax dslr support both sdm and the motor inside the body. earlier sdm lenses support both systems as well. the first sdm lens that did not support the old focusing system was the da 17-70/4 al [if] sdm (2008).