VR or vibration reduction is the Nikon term for image stabilization. Nikon has introduced two generations of VR which they have logically called VRI and VRII. For VRII Nikon claims up to 4 stops of improvement. It is my experience that the minimum shutter speed to consistently achieve sharp images is the reciprocal of double the focal length. For example with a 200mm lens this would require 1/400 sec handheld without VR to produce 90% consistently sharp images. A 4 stop improvement would be 1/30 sec with VR, which is darn slow to handhold a 200mm. It is always good to test such claims to see if they apply to oneself - a combination of individual technique and equipment. So, that is what we are going to do here.
The test used a D700 and 70-200 VRII lens set at 200mm and the target was 9 meters away. Focus was set once at the start of the trial using live view. The camera was set in shutter priority mode and 10 exposures were taken for each shutter speed, varying from 1/500 to 1/4 sec. Aperture and ISO were adjusted to keep the exposure constant. Aperture was f/4 or larger, as I did not want to risk possible softness introduced shooting at f/2.8 although the 70-200VR lens is quite sharp wide open.
One quirk in the test was that I originally planned to test from 1/500 to 1/15 sec, but the results were so good at 1/15 sec that I added 1/8 sec and 1/4 sec. In order to expose for these lower shutter speeds I added a neutral density filter and shot later in the day. The camera was set to record JPG fine images and the auto WB color cast changed between the first and second shoots, explaining the difference in colour in the test result. This does not affect the test as the issue is how sharp are the photographs.
From this test we can conclude that Nikon's claim of a 4 stop improvement is correct, and a bit of softening starts at 1/15 sec and it is hit and miss at 1/8 sec and 1/4 sec. Amazingly, one of the 1/4 sec shots, the third, is very sharp.