TechNotes: Video Performance Factors

Video Performance FactorsThe goal of every TV is to accurately reproduce the image that was captured by the camera. There are four primary factors that contribute to our perception of video quality. Proper calibration will have a dramatic affect on the top three of these four factors. Here they are, in order of importance:

  1. Contrast
  2. Color saturation
  3. Correct color (colorimetry)
  4. Resolution

The difference between a bad TV and a great TV is often the calibration that occurs after installation. All of SoundVision’s technicians are professionally trained TV and projection system calibrators, so it’s guaranteed that any SoundVision system will operate at peak performance from day one.

Contrast – Also known as black level, contrast measures the difference between a TV or projector’s black and white light output and is measured as a contrast ratio of white light output to black light output and is one of the most important of the four factors. In a perfect world, we’d see zero light for black and very bright light for white. For example, a very high contrast ratio measured in a commercial theater might be as high as 300:1. We typically measure contrast with a black and white checkerboard pattern displayed on screen, and observe the differences between the white squares and the black squares.I know you’re asking,”But Scott, what about TVs with advertised contrast ratios of 10,000:1, 50,000:1, or even 150,000:1?”  The answer to that simple: it’s marketing. While contrast is very important, you really can’t take a manufacturer’s specification of contrast ratio seriously. For the ultimate in contrast, it’s best to have your new TV or projector professionally calibrated by experts.

Color saturation – A TV or projector’s ability to reproduce deep, rich colors is called color saturation. However, there’s something to be said for striking a balance between undersaturated and oversaturated colors–with the latter resulting an artificially bright image. And while some TVs are better at producing deep colors than others, perfect color saturation is something that can only be truly achieved by a professional calibrating expert.

Color correctness – The color video signal we see is actually made up of a combination of red, green and blue. When our TVs display the correct amount of these three primary colors, the image appears correct and natural. However, if the level of just one is incorrect, you will instantly see something wrong with the picture. Many manufacturers and retailers will increase red and blue levels in order to make a TV appear brighter on a showroom floor. While it succeeds in producing a brighter image, often times this tweak results in an unnatural, almost cartoon-like appearance. Proper color correctness, or colorimetry, can have a huge impact on your TV, and it’s something that is best to be left to the calibration experts.

Resolution – Simply put, resolution is the number of pixels the display can use to re-draw the image. The more pixels a TV can reproduce, the more detailed image it can display. Here in North America, there are five common levels of resolution:

  • 480i – 480 lines of resolution, interlaced scan (regular standard-definition TV)
  • 480p – 480 lines of resolution, progressive scan (DVD-quality enhanced definition)
  • 720p – 720 lines of resolution, progressive scan (broadcast HDTV – Fox, ABC, ESPN, etc.)
  • 1080i – 1080 lines of resolution, interlaced scan (broadcast HDTV – CBS, NBC, etc.)
  • 1080p – 1080 lines of resolution, progressive scan (Blu-ray Disc)

Of those, the last three HDTV formats are the ones that dominate the video landscape today, with 1080p coming into popularity as Sony’s Blu-ray Disc technology gains market share. There are two factors at work in each of these specifications–the first is the number of lines the TV can draw (more is better), and the second is progressive and interlaced scanning methods. Interlaced formats such as 1080i draws even lines in one frame and odd lines in the next, which can sometimes lead to motion artifacting during action-packed scenes. Progressive scanning redraws the entire screen on every frame, which is why it’s the superior format, especially for live-action sports and other motion-intensive programs. And while resolution is an important factor when choosing a new TV or projector, most experts agree that resolution needs to be doubled for the human eye to discern a difference in resolution.

TechNotes is an ongoing feature on the SoundVision Blog where SoundVision’s Scott Sullivan answers questions and shares some of the technical details behind the home entertainment and control industry.

Have a question you’d like Scott to tackle? Send him an email!

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