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Evaluating Your Video Display
Display Performance Home Page
This section of WalVisions serves as a bridge between the Home Theater and the Test Pattern sections. Here we discuss the evaluation of video displays, and delve into the meanings and relative importance of the various display functions and specifications. As with all of WalVisions,
we anticipate that this section may evolve over time, so we encourage you to check back regularly. If you have any comments or suggestions, please
contact us
here.
There are a number of independent factors that go into the overall performance of a display, and while they are all important, some are more crucial to excellent performance than others. We hope to provide sufficient discussion and comment so you will be able to judge for yourself the strengths and weaknesses of the various display types. Hopefully this section will help you better understand display performance issues, and thus you will be more confident in selecting the best display for your home theater application.
Just how important is the display performance to your home theater? Only you can decide, but we hope to help by pointing out the various factors affecting performance, as well as some parameters and methods in which displays are evaluated. The home theater buyer/owner has to decide for himself just how to weigh each factor - this is subjective and can vary greatly from person to person. For example, when you walk from outside into certain stores with poorer
fluorescent lighting, do you notice how colors just aren't correct and natural? If you wear glasses - and,
even if you don't, you likely have had the same experience with sunglasses - how much do dirty lenses detract from what you are seeing? How bothersome is looking through a dirty windshield or window? When you walk down the street how much does debris on the side of the road detract from your enjoyment? Do you notice that a neighborhood without telephone poles is more pleasing? Does it bother you when you have to strain to see in darker restaurants? In ways similar to these examples, the higher levels of display performance improve the viewing experience. For the enhanced experiences you will need to spend a little more time in thoughtful evaluation, and usually you will spend more money, but you should get ample payback in the satisfaction of years of viewing pleasure.
The first performance category we address is
Geometry, Focus, Registration. This goes into the size and shape of the image, the quality of focus, resolution and the registration of the three colors to each other.
The
Luminance and Contrast section evaluates the display's luminance parameters - how bright are the white levels, how black are the black levels, what is the full field contrast ratio, and what is the dynamic (ANSI) contrast ratio?
The
Color Temperature, Gray Levels section addresses the basis for color fidelity in the display. Are the "black and white" parts of the image truly colorless, are they at the correct level for the various input levels, and are the levels the same over all screen areas? Here we attempt to help find the answers.
We next go into
Dynamic Performance, which focuses on how the display stands up to changing scenes. It's one thing to be able to make good images with a static, unchanging image, but can be quite different with rapidly changing images. The various display technologies can perform quite differently - here we try to point out some of these differences.
We then look into the
Video Processing aspect of display performance. We discuss deinterlacing, film "3:2 pulldown", image enhancement, image scaling, and color decoding. All these processing stages can have noticeable effects on the performance of the display.
Lastly we go into
Display Defects and Artifacts. Dead pixels, dust, the screen door effect, and aliasing can all detract from the ultimate image performance. We provide some guidance in finding and evaluating these potentially troubling characteristics.
Please be aware that we will make frequent references to the test patterns here at
WalVisions, as they can be very good for illustrative and evaluation purposes. Ideally the display device in question can display
Internet pages, but even if that is not possible, we think that simply viewing the patterns on your PC display will be very educational. For best display the patterns should be viewed in full screen (usually selected by using the F11 key in your browser).
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