Scopes

The aim of this document is to give the reader a clear understanding of the basic functions of the different Scopes used in Broadcast engineering. The purpose of using a scope is to give the user a graphical representation of the video signal. Using the scope you can make judgements about how the imaged is exposed and whether the colour balance is correct. You can also judge one signal against another which is a vital part of the line up process. You can find more information about the line up process here. The topics that will be covered in this document are:

Types of Scopes and their purpose.
Description of Histogram
Description of Waveform
Description of Parade
Description of Vector
When to use them

Types of Scopes and their purpose

HISTOGRAM - Understanding a histogram allows you to judge whether an image is over or under exposed, whether the lighting is hard or soft and what adjustments need to be made. Each pixel in the image has a value for it's brightness, this value is displayed on the histogram. The brighter a pixel is the further to the right of the histogram. At the very far right of a histogram you have pure white and at the other end pure black. So the left / right axis is all to do with brightness distribution or luminosity of the image. The more pixels there are in any particular area the higher the peak on the histogram. If you have a very bright image there will a peak high in the right hand side of the histogram. It's worth noting that where the pixel appears within the image bears no relation where the information appears on the histogram.

The image above is obviously brighter on the left hand side but notice how the information for the dark areas of the image appear in the left hand side of the histogram. We can tell by reading the histogram that the image is fairly well exposed with a big spike in the 'Shadows' section.

Report abuse