Sample hold effect: A vertical line, which consists of individual pixels one below the other, can be drawn on a LCD- Or Plasma-Show TV cleanly. The edges appear sharp, the line is clearly recognizable. The situation is different when the line moves across the screen. Now it's fuzzy, especially on LCDs. If you take about one Full-HD-Display with 1.920 pixel pros row and a tempo of ten seconds from the right to the left edge - not even particularly fast - then the line sweeps 192 pixels per second, but there are no more than 50 frames per second. The line must therefore jump by around four pixels from image to image, while its one-pixel dimension remains unchanged.
What changes, however, is the impression that the line leaves on the viewer's retina: the viewer follows the object with his eyes and sweeps four pixels over the 0,02 seconds of an image. The vertical line looks four times as wide on the retina, i.e. drastically less sharp. It's like a still photo: if you hold the camera still, the line remains a narrow line (if the exposure time is less than a fiftieth), but if you follow the object with the camera, it is photographed blurred.
This so-called sample-Hold effect can be reduced or eliminated with different strategies. Depending on the screen technology, it is more or less visible. Devices with a dark phase between the images, such as projectors, fool the eye into seeing a sharp contour, blurring is less noticeable.