V for Vibration Reduction (VR)
VR, is also known as IS (Image Stabilization) in Canon lens, is a system of arrangement of lens and motor which constantly moves the lens elements to compensate for the tiny hand vibrations. It becomes visually significant in slower shutter speeds and at extreme telephoto focal lengths. Normally they allow for 2 or 3 stops worth of stabilization. On the downside, when taking long exposure photos, on a tripod, the lens may try to compensate and actually cause blurring. Contrary to certain beliefs, keeping the VR mode on, hardly drains the battery in an excess, but the advantages are immense.
This is a part of April AtoZ Challenge. Previous letters, right here.