Nikon has always used the finest glass possible to manufacture its lenses, including its less expensive line of lenses. Now, Nikon's VR lens line uses internal anti-vibration technology instead of in-camera technology. What are the advantages? Inside every VR lens sits two voice-controlled motors and two sensors. The sensors determine the amount of pitch and yaw present and uses two separate algorithms to correct any discrepancies. The first algorithm used is weaker and takes place when the shutter is released half-way. This allows the image to stop "shaking" in the viewfinder and also helps with spot-metering functions (spot metering relies on accurate placement of the meter on the subject). The reason the first algorithm is weaker is to prevent the feeling of sea-sickness when viweing the image through the finder. When the shutter is released all the way down, the sensors make any final adjustments, the algorithm changes to the actual image correcting algorithm and the motors adjust accordingly. Why is this a USP? Because systems that use in-camera image stabilization or VR-reduction make adjustments to the image by moving the sensor during exposure, which means the image in the viewfinder remains unstable--making composing and accurate metering more difficult.
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