Why Is Black Level So Important?

A TechLore "Ask the Experts" Question...

Question:

I'm currently deciding whether to purchase a DLP/Plasma/LCD, and I want know what black level actually is? I know it has something to do with brightness... Is there any distinction between brightness and black level, or is it just a synonym?

-submitted by Spikey84

Answer:

Brightness and black level do go hand-in-hand, and sometimes the terms are interchangable. You'll often see the brightness control on a TV referred to as "black level". Think of this more as a term used to describe adjusting the way a TV displays low level details to achieve accuracy.

When shopping for a TV, the term "black level" takes on a slightly different meaning. Think of this as the displays ability to create the color black, and distinguish detail in very dark images. Many displays can't display the color black, and this absolute threshold is a key factor to image quality because if the TV's darkest black is some from of dark gray, subtle dark gray details will fade into the background. Look at these two pictures for example.

The image on the left is a perfectly black background. On it are two black stripes, each a little brighter than the other. The image on the right is what happens when the darkest black the TV can produce is not absolute black, but more of a gray. The top bar is still there, but now invisible because it got swallowed into the background.

As another fun test, you can see what happens to dark details when you set the brightness of your display too low. While watching the left box, reduce the brightness on your monitor. Watch how the top box becomes lost in the background.

 

If you want to see those details on TVs with a poor black level, you can try to increase the TVs brightness control to make the swallowed image become darker than the background, thus making the details in the lower range visible. The problem with this is that by increasing brightness, the image starts lose dimension and becomes washed out, and you'll lose detail at higher gray levels. On top of this, details that were supposed to be subtle now become obvious and irritating.

If you look at these images above from one of my favorite shows, 24, you'll see how black level alters the entire feel of the scene. In the first picture, Tony is slightly drawn into the background, and is listening intently. The dark feel accentuates the mood of the scene. When brightness is ramped up, Tony looks more confused, and things in the background that were not supposed to be visible now are. Notice how the entire mood changed? Now it looks Like Tony is listening for instructions on how to bake a pie.

Black Level is crucial to getting a three-dimensional, realistic, and detailed picture. Anytime you're shopping for a TV, make black level one of the factors that help you consider what to buy, but make sure the brightness and contrast are properly adjusted before making your evaluation in the store using a test DVD. A test disc like Avia or Video essentials would be ideal, but the THX optimizer on many commercial DVDs will work in a pinch. Also bring along your own material to use as a test. Use material with lots of dark details (24, Lord of the Rings: The Two Towers, and Thir13en Ghosts are discs I commonly use, but there are many other good ones) to evaluate how each display handles real-life content.

Currently, only the best CRT displays will be able to display a true, rich black, but some of the nicer DLP, LCD, and plasma products will do a good enough job to give a great picture. In the end, the more attention you give evaluating black level, the more satisfying your experience will be.

Matt Whitlock - Editor, TechLore.com

Did You Know...

There are many different kinds of TVs in the marketplace today. Find out what makes all of them different by reading the article series "How To Find the TV that is Right for You".

While You're At It...

Take a moment to get that image looking its best by adjusting your TV's video controls. Read "How to use your television's video controls" to help you get that picture looking perfect.

Is your TV screen covered with dust, dirt, and grime. It's time to clean, but cleaning it the wrong way can damage the screen or cabinet. Read "How to Clean Your TV Screen" to learn more.

 

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