Image Stabilization

[Proteus]

When I use my brush my mortars using my electric toothbrush and watch the clock of my microwave oven, it vividly vibrates due to the vibrations of my skull, yet when I turn off the light and look at the light of my printer, it's perfectly still, even though the surroundings appear totally dark. Why does my brain react differently to the numbers of the clock than to the light of my printer? Why do only the numbers vibrate, and everything else in the environment, even if isolated in darkness, appear still? Is this an optic effect, caused by a possible lower frequency in the light of the clock, or some kind of neurological or other effect, perhaps caused because my brain interprets the numbers as concepts rather than ordinary visual input?