One key aspect to how well the picture appears on your screen is the contrast ratio. The colors on your screen and how the extremes of brightness to darkness contrast to each other can make or break your viewing experience. If a television has a poor contrast ratio rating, there will be a dramatic reduction in the true blacks and there will be a visible saturation of colors.

The contrast ratio of your DTV works hand-in-hand with the screen resolution to give you a picture that looks painted onto your television. The larger the screen resolution and the higher the contrast ratio the more breathtaking the image will be. You’ll be in DTV heaven!

The photo shown above is an example of what two extremes of contrast ratios (e.g., left – 9,000:1 and right – 1,000,000:1) might look like to a viewer. Each screen looks great individually but color differences become immediately apparent when doing a side-by-side comparison.

A television’s contrast ratio is measured by numerically grading the shades of the brightest whites to the shades of the darkest blacks and then putting that information into a ratio of luminance. But, what exactly is luminance?

LUMINANCE
The contrast ratio of a DTV is defined as the ratio of the luminance between the brightest color (white) to the darkest color (black) that a particular television is capable of producing.

It is a measure of the luminous intensity per unit area (nits*) of light travelling in a given direction. For DTV purposes, it identifies the amount of light that is emitted from the television screen and will be perceived by iris of the human eye. The flat and diffuse surface of a DTV is perfect for characterizing the emission of luminance from the screen. Essentially, the luminance is a really good indicator of how bright the screen’s surface will appear to you; the viewer.

MEASUREMENTS – Full ON / Full OFF
Most LCD, plasma, and projection DPS televisions are graded using the Full ON / Full OFF method of measurement for determining each individual set’s contrast ratio. This measurement uses the ratio of the light output of an all white (Full ON) image to the light output of an all black (Full OFF) image.

The core reason for manufacturers opting for this method is because it removes the room the television is in as a variable, resulting in an ideal ratio. As long as the room’s conditions stay constant, equal amounts of light will reflect back in both the white and black measurements, leaving the luminance (white to black) ratio unaffected and true.

RATIO
The contrast ratio is comprised of two numbers separated by a colon. The number on the left is the brightest white, the colon means “to,” and the number on the right is the darkest black.

In the contrast ratio shown above, the numbers explained mean the color white is 40,000 times brighter to the darkest color of black. But, the black number is even more important than the white number. That’s because reducing the darkest shade of black on the screen by just 0.5 will effectively double the overall contrast ratio. 

DYNAMIC vs. NATIVE
Some contrast ratios are displayed with two contrast ratio results; one listing dynamic and one listing native (on screen).  As a general rule of thumb, the dynamic contrast ratio is approximately 10 times that of the native contrast ratio. For example, a television’s specification sheet might list the dynamic contrast ratio as 25,000:1 and then immediately list the on-screen contrast ratio as 2,500:1.

Dynamic = the contrast ratio between the brightest white (with brightest backlight) to the darkest black (with darkest backlight). It can be difficult to discern main features that are blending into the background during very bright (daytime) or very dark (nighttime) scenes. Dynamic contrast ratios can control this issue by adjusting the backlight intensity accordingly.

Native = the contrast ratio of the brightest white (e.g., 500 nits) to the darkest black for a fixed intensity (for both white and black) of backlight.

ROOM CONDITIONS
Ideally, the room to watch your DTV will be in total darkness; just like your local cinema. They understand more than anyone that contrast ratios and brightness are directly affected by the ambient light in the room. Not only do cinemas turn the lights off when the movie is queued up, they have no windows and have minimal lighting in the form of recessed runway LEDs along the edges of the staircase. They want it as dark as possible.

The darkness is also the ideal condition for manufactures to test the contrast ratio of their televisions. The testing room is not only free of any surrounding lighting; it is also without any obstacles (e.g., furniture and people) to reflect the light emitted by the television’s screen. This would mean 100-percent of the light rays are completely absorbed by the room and the only light displayed would be from the monitor itself.

OTHER TESTING METHODS
Some manufactures have developed features that adjust backlight levels in realtime which boosts the native contrast ratio to a higher dynamic contrast ratio. Sharp has named their feature Spectral Contrast Engine and Sony has named theirs Advanced Contrast Enhancer. These features perform image processing to adjust the contrast in addition to optimizing the backlight levels.

The Full ON / Full OFF method is the most common and widely used form of measurement for determining contrast ratios in DTVs. If you are shopping and the contrast ratios just don’t seem right, ask your HH Gregg sales associate what method was used to measure contrast. Other forms of testing are: 

• American National Standards Institute (ANSI)
• Video Electronics Standards Association (VESA)
• Japan Electronics and Information Technology Industries Association (JEITIA)

FINAL THOUGHTS
Your contrast ratio is an important specification you should check for when shopping for a television. After all, isn’t the stunning contrast of colors on the screen what makes your eyes come alive in the first place?

Judge the contrast ratio with the numbers and your eyes. The human eye can recognize the contrast ratio of a screen much more clearly than resolution. This is why a 1080p (1920 x 1080) screen with a low contrast ratio rating might not look as good as a 720p (1280 x 720) screen with a very high contrast ratio.

Still have questions? – feel free to speak with an hhgregg associate. We offer the best-educated associates in the business who are smart enough to make it simple. Price and Advice Guaranteed!

This entry was posted on Tuesday, March 3rd, 2009 at 2:20 pm and is filed under TV & Video. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.