Plasma Display Contrast Ratio Explained

Many factors contribute to your satisfaction with a big-screen home theater display.  Contrast ratio, while important, tells just part of the story.  Other factors range among picture size, peak brightness, color accuracy, signal processing, motion handling, resolution, and pixel aperture ratio (fill factor).  Meanwhile, your viewing environment and room lighting affect perceived quality in many of these areas.  For instance, room lighting has a dramatic affect on contrast ratio.  Bright rooms sharply reduce perceived contrast.

Contrast ratio (CR) is defined as the difference of luminance energy measured from the brightest white and then compared to the luminance energy measured from the darkest black of a particular device or a particular environment. 

How do we measure contrast ratio?
Test patterns with all-white and all-black areas are put on the screen.  The light energy from the areas is then noted.  For example, if the white area is 1000 candelas and the black area is 1 candela, the screen is said to boast a 1000:1 contrast ratio. 

What is the testing environment?
Engineers test CR in a pitch-black testing room; otherwise, ambient light lowers the measured ratio.

What about the contrast ratio of other displays in typical viewing environments?  In other words, what contrast ratio are we already accustomed to?          

•       Your office computer's CRT, in office lighting, has a CR of only 20:1.

•       TV in our living rooms, with subdued evening lighting, will net a CR of about 60:1.

•       Projected movies in good theaters - considered the most satisfactory "display device"
  - typically deliver a CR of 180:1.

We see that familiar display devices satisfy us with relatively meager contrast ratio.  Couple this with evidence showing we humans, once our eyes adjust to the brightness of a new environment, still only perceive a maximum CR of 100:1. 

Then why do new Fujitsu monitors, measured at 1800:1 contrast ratio, look so good next to other plasma sets measured at 5000:1 CR?
Our 55" plasma looks brighter than competing designs, because it's made differently than standard plasma sets. To explain why it looks so good, let’s first review how standard plasma displays – including our 50” award-winning plasma – make their pictures. 

In a typical plasma display, rows of tiny lighting dots alternate with rows of jet-black masking material. This masking is darker (reflecting less light) than the dots, even when the set is turned off and no dots light up. This super-dark masking improves contrast measurements, but limits the height of the lighting dot within each pixel, in turn limiting potential screen brightness.  Also, the mask worsens the "screen door effect" when you view from distances closer than 7 feet.  Finally, due to the small size of the lighting phosphors, the primary colors wear at different rates.  Colors shift easily and need adjustment more often. 

Fujitsu's 55" plasma design, featuring the e-ALiS (Extended Alternate Lighting of Surfaces) driving method helps our Plasma engineers make this set brighter, simpler, and longer lasting.  Here's why: 

1.   The e-ALiS  phosphors stand taller. So the lighting phosphor area nearly doubles.

2.   The e-ALiS driving method lets the panel drive light from all the phosphors, every video field, with only half the standard number of electrodes and drivers.

3.   No masking is needed because all the parts of the phosphor column light up. With the black masking gone, video measuring devices generally report lower contrast ratio figures for e-ALiS screens. 

But does the non-masking e-ALiS method cause picture quality to lessen?  No. The extra brightness makes the picture look better!   

Internet resellers - and big-box resellers' ad writers – have no showrooms to let you compare picture quality.  That’s why they depend heavily on numbers.  However, when your Fujitsu custom a/v dealer shows you Plasmavision display’s stunning picture quality, you can believe your eyes.   This is where the Fujitsu 55" Plasmavision display really shines.