What does a frequency of "X" Hz mean in LCD or Plasma TV or LED TV?

Introduction to 50Hz televisions

A regular PAL television changes the picture at a frequency of 50 Frames Per Second (FPS) or 50Hz. The illusion of movement in the picture is produced by the successive frame changes of the picture 50 times per Second. A 50 FPS (50Hz) Cathode Ray Television (CRT) creates the picture with an electron scan and there is a visible flicker that is sensed by the human eye.

The Human eye is at occasionally sensitive to this frequency depending on the intensity of darkness, the speed of the image, and the degree of brightness thus you will occasionally notice the picture flicker on a 50Hz TV. The flicker becomes more apparent on larger screen.

Early 100 hertz technology

A 100 Hz TV operates at twice the Frames Per Second (100FPS) by producing a replica of every frame and inserting it after the previous one. The result of this doubling of the scan frequency to 100Hz and inserting a copy frame is that this problem was eliminated as far as the eye perceived it. The result of this is to significantly lower the flicker.

How does 100Hz work on LCD and Plasma TV?

LCD and Plasma televisions don't produce flickering because they don't produce the picture with an electron scan. However LCD TV's still benefit from 100Hz because advanced digital circuitry creates an extra frame or middle image. This is done by the TV inventing an extra frame using complex interpolation and motion compensation calculations to work out what the extra fields and frames look like rather than inserting a replica frame. (e.g. the second frame is not the same as the first frame).

However even at 100 FPS the picture still does not deliver a entirely smooth picture particularly with fast motion images. Some television manufactures attempt to reduce this further by employing digital picture processing. Typically there is still a little blurring on quick moving images but the benefits are clearer and better-defined surfaces, sharper pictures, and smoother movement than is possible from 50 Frames Per Second Plasma and LCD televisions.

i.e. if a football moves ten pixels from right to left between frames one, two and three, the 100 Frames Per Second television will digitally create two added frames between one and two, along with two and three, in which the ball will travel five pixels. This therefore results in a total of five frames in which the ball moves a total of ten pixels i.e. the original frames one, two and three plus the digitally created frames that are inserted in between one and two, and between two and three. The eye thus sees a picture that moves more fluidly than before.

The benefits of 100 Hz

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.

200Hz, 400Hz, 600Hz and now 1200Hz

Once Sony launched a 200Hz range which digitally inserts three additional frames between the original 50Hz frames we have seen the market go into overdrive with manufacturers aiming to give the maximum amount of Hertz possible. Overall though the effect of this is that we are seeing fast moving sequences being delivered with a amazingly smooth, more fluid and sharper images than ever before.

Backlight Blinking

XR200, XR400 and XR800 plus Panasonic`s backlight blinking technology has seen a slightly different slant to the traditional refreshing of the image. Whilst the image is cycling at 100Hz or 200Hz, out of phase or in between each frame the LED back light is actually turned off momentarily. This essentially introduces a blank, black frame in between the coloured image frames. This has the effect of creating a black back drop to the coloured image and when cycled very quickly it has the result of further emphasising the colour, whilst also improving the motion handling.

The added benefit for people with photosensitive epilepsy

Scientific studies have proven that for patients with photosensitive epilepsies 100Hz and 200Hz televisions can help prevent seizures when playing video games or watching TV.