If you look at a fully blur-corrected image through a viewfinder for a long period of time, you may start to feel discomfort as if you were suffering from car sickness. To prevent this, Nikon developed an algorithm exclusively used during half-pressing of the shutter-release button. The algorithm suppresses blur correction at a slightly weaker level than usual so that you can comfortably continue to view the subjects within the viewfinder. When the shutter-release button is fully pressed, a different algorithm is employed, so that the blur-correction effect is maximized during exposure, providing the clearest results.
* Taken with Nikon D7000's D-Movie