An Introduction to 50hz tv pictures
Ordinarily PAL televisions will refresh the picture with a frequency of 50 Frames Per Second (FPS).The Frames Per Second (FPS) are the number of frames required to generate the illusion of motion. On a 50 FPS (50Hz) Cathode Ray Television (CRT), due to the picture being produced with an electron scan, there is a visible flicker that is seen by the human eye.
Our eyes are at times are sensitive to this frequency depending on the speed of the image, the level of darkness, and the level of brightness so you will sometimes notice the picture flicker on a 50Hz TV. Also the larger the screen is the more noticeable the flicker is.
How 100 hertz used to work
A 100 FPS (100Hz) television operates at twice the Frequency by creating a copy of each frame and putting it after the one before. As a result of doubling the scan frequency to 100Hz and inserting a duplicate frame this effect is eliminated, as far as the eye is concerned. The consequence of this is to drastically lower the flicker.
100hz on LCD and Plasma tv’s
Plasma and LCD TVs dont have flickering as they dont generate the picture with an electron scan. But LCD TVs are still able to benefit from 100Hz since cpmplex digital circuitry creates a middle image or an extra frame. The TV does this by creating an further frame by means of complex interpolation along with motion compensation calculations to work out what the addition frames and fields look like instead of inserting a copy frame. Therfore the first and second frames are different.
Nevertheless even at 100 Frames Per Second the picture still does not show an absolutely smooth picture especially with fast moving images. Several television producers attempt to reduce this further by using advanced digital picture processing. Typically there is still a little blurring on quick moving images although the benefits are sharper pictures, clearer and better defined surfaces, and smoother movement than is possible from 50 FPS LCD and Plasma TVs.
e.g. For a football that travels ten pixels from left to right between frames one, two and three, the 100 hertz TV will digitally create two further frames between one and two, and two and three, between which the ball will move five pixels. This will result in five frames where the football moves a total of ten pixels i.e. the original frames one, two and three plus the digitally created frames inserted between one and two, and in between two and three. The result of this is that the eye sees an image that moves smoother than before.
100 hz is a benefit
The benefit is that 100Hz televisions have a clear benefit of ending a lot of the ghosting effects sometimes seen in LCD TV’s. The ghosting effect caused by the new image being displayed before the previous has faded away. The created middle frame also benefits the Plasma television picture by make the picture more fluid and natural.
Most top manufacturers have now got 100Hz LCD and Plasma televisions including Panasonic, JVC, Samsung, Toshiba, LG, Sony, Philips, Pioneer and Hitachi.
Sony lead the way into 200Hz
A range of 200hz TVs have been produced by Sony which digitally inserts three further frames between the original 50Hz frames. Hence speedy moving sequences are delivered with a more fluid, sharper and smoother picture than 50 hertz or even 100 hertz TVs.
Additional benefit for photosensitive epilepsy sufferers
Research has proven that 100 hertz televisions can assist in preventing seizures in people who suffer with photosensitive epilepsies when viewing television or playing computer games.
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