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What Is Chrominance?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 03 November 2014
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Chrominance is the part of a video signal which carries information about the attributes of the colors being displayed. The development of a technique for transmitting information about color paved the way to color television, a move which revolutionized the television industry. Color values are given in the form of quantitative measurements against a standard reference color so that the signal is standardized, although properties of the display screen can change the way in which the color expresses. People may use the term “chroma” to refer to chrominance.

Two different properties are expressed in the color part of a video signal, the hue and the saturation, with the color being defined by the red, green, blue (RGB) color metric for a quantitative description of the color. This information is also bundled with luma, which refers to brightness. Since the human eye is very sensitive to differentiations in brightness, chroma and luma can be balanced against each other to achieve a crisp, clear image with recognizable color patterns.

Sometimes people experience what is known as a chrominance to luminance delay, usually because of problems with a broadcast. In this case, the color signal lags slightly behind the brightness signal, and as a result colors may appear smeared or runny, especially around lines. This can be very distracting for some viewers, as even when the delay is not readily visible, it can trick or confuse the eyes.

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When problems are identified with the color part of a broadcast, it may be due to the broadcast itself, problems with the equipment, or issues with the image processing. Television networks generally try to address problems with broadcast quality as quickly as possible, to avoid losing frustrated viewers who turn off the television when signal problems persist.

This term is also sometimes used among photographers when describing image processing techniques. All cameras generate varying degrees of “noise” in the images they take, and image processing often includes cleaning up the images so that they look crisper and more visually pleasing. However, because people are more sensitive to variations in brightness than in color, processing for chrominance noise reduction must be done with care to avoid compromising the finished image. Digital programs for image processing split the image into chroma and luma components, allowing people to clean up the chrominance without sacrificing luma at the same time, keeping the image crisp with clear contrast, especially in the rear of the image.

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SZapper
Post 2

@strawCake - Interesting. I actually ended up with a set of photos with digital noise and it was not pretty! These were just supposed to be snapshots though, not abstract art!

I'm pretty sure I've seen chrominance to luminance delay. Not recently, but back when I was younger before digital cable we just had a really basic package, complete with bunny ears! Suffice to say, the picture didn't always come through so clearly.

strawCake
Post 1

When I was in college studying photography I learned a little bit about digital noise. Quite by accident, actually! I made an abstract photograph that had some digital noise in it.

I actually like the effect on that particular piece but I can see how it would be undesirable on a regular photograph. But for abstract pieces of art digital noise can act as a design feature.

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