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Sound Television Graphics Act 3 Pretest

Remember we said: "The "talking head shot" is 90 % of what you see on television because television sets, and often projectors just cannot reproduce fine detail. Body language isn't able deliver the same effect as facial expressions to best support or tell the story." One might say that HD is changing that need for these extreme close-ups somewhat. However, there is no better way for the audience to tell is someone is lying (for example), or how they really feel but to read their face.

The technology for producing video images is so rapidly evolving. Video files are very large which make them hard to store, upload and to be put to use. As a result, the files need to be compressed. The end result's are called "codecs.".  Common Codec arcane names are MPEG-4, and H.264, and RS422. Codecs are digital formats that are like digital languages that can only be understood by equipment designed/programmed to read them.

"Click">>>How TV Works<<< So basically the moving picture you perceive to see on your screen starts with rows of very tiny sparks of light that light up in succession for a very brief moment, one at a time and at an extremely fast rate. There is a brief after glow, but the individual flashes are so fast that our brain perceives a lit image or a whole picture. Imagine the dots appear as letters you look at on a page as you read, but each letter is exposed one letter at a time, left to right. Your memory allows you to interpret the individual words as they progress and then into sentences one line at a time. However the rate that you are reading the page is so rapid that it seems that you are reading the whole page at a glance.

It may be hard to believe, but the screen that you are looking at, lights up only one dot of light at any given moment in much the same manor. Each spark of light goes off in sequence left to right, in a row or line, one line at a time, but at such a rate, combined with the after glow, we interpret the the whole screen as being lit all at once. This rapid sequential firing of light is called scanning. The one difference is that scanning lights up each odd numbered line ( left to right of course) starting at the top and working down the screen. Then repeats the same procedure with all the even numbered lines.              

The individual sparks of light are referred to as Pixels. A pixel is the smallest single component of a digital image. It is represented by a
 number for its color and brightness value
. Dots per inch (dpi) and pixels per inch (ppi) are sometimes used
Computers record images as a series of numbers that represent each pixel.  To display the image the
 computer converts the number to the colored pixels.


As we mentioned in an earlier section, there are only three colours (red, green and blue) lights flashing that make up all the colours you perceive to see on your screen. If we magnify the screen to the extent that we see the individual pixels, you should notice that they are actually rows of red, green and blue dots. What happens as the scanning is going on; is that the dots light up with different intensities, again combined with some afterglow effect, the process is like mixing paint in our head and we visualize all the colours of the rainbow.

The number of pixels in an image is sometimes referred to as the resolution, although resolution has specific definition. Resolution indicates the size of the component that make an image. Resolution units may be in lines/inch or lines/mm, as well pixels/inch. The result is that resolution affects the detail or clarity of an image.  Pixel counts can be expressed as a single number, as in a "three-megapixel" digital camera, which has a nominal three million pixels, or as a pair of numbers, as in a  "640 by 480 display", which has 640 pixels from side to side and 480 from top to bottom
 (as in a
VGA display), and therefore has a total number of 640 × 480 = 307,200 pixels or 0.3 megapixels.

The size of the pixels is determined by the size of your screen and the number of lines that the screen is broken into. The standard number of lines in North America on most equipment is 525 lines. The more lines on a screen, results in a higher  resolution by making more and smaller pixels with in a space to produce your image. As a result; Resolution determines the clarity or crispness of an image.

Clarity of the picture is also affected by the strength of the signal. A poor signal or one that has
interference, can produce noise, or a snowy picture. The signal is always competing with the background static coming from your TV set or within your projector. The background static was significant when TV's  had app a foot and a half of electronic components behind the screen compared to today's flat screens. White noise, salt and pepper picture, is the picture you see when your local TV station goes off the air, or if there is simply no signal. Noise in a picture was especially common when we relied on analog TV transmissions through TV aerials. Noise is not limited to picture, but also with audio. There was a 2005 scary movie built around the phenomena of white noise.

In essence, Video is a series of still information which is displayed so rapidly that, due to persistence of vision, the eye and brain perceive motion.

So once we establish that still information, Frame rate is of importance to ad that perceived motion, especially smooth motion. Television and movie motion pictures are actually a series of still images that your eye interprets as motion. The viewer  will perceive motion if a viewer's eye sees at least 16 images per second in rapid succession. For technical reasons, the most common frame rates used in modern television and movies are (approximately) 24 frames per second and 30 frames per second, abbreviated 24 fps and 30 fps. This is easy to visualize if you ever saw an old real to real projection or if you consider how we make animations.

ASPECT RATIO is the proportional comparison between the width and the height of a picture.

Unlike the printed page (which can be almost any shape) television images, used to have to fit a 4 x 3, now must fit in the 16 x 9 ratio of HD television and 21 x 9 for theatre. This is important to realize as a mishmash of source and screen would result in one of 3 scenarios. For example if a 4/3 picture is displayed on a 16/9 screen

  •  If the perpendicular dimensions fit the screen, the horizontal dimensions of your picture will fall short leaving black unused screen.

  • Otherwise, in order to fill the screen, your image has to be stretched. This distorts your image.

  • The third option is to crop some of the picture. So if your image is zoomed in till the horizontal dimensions fit the screen, and you don't distort the picture, the top and bottom have to be cropped.

The results would be even more obvious if the old standard were being displayed on a theater/movie aspect ratio.

Aspect ratio is a good reason to be aware of the Safe Area of your image. To insure that a desired part of your image is not cropped off when your image is presented. Always have a buffer zone, a portion of your image if cropped in any direction, that would not impede on the visual you are wanting to deliver.

You may have intended to show this as illustrated your original cut , but what ends up on your screen is often not exactly the same as the original. Keeping the important aspects within the safe area avoids disappointment like the one on the right>>



1.) How is the picture on your TV image produced on your screen?

2.) How do pixels effect the CCD?

3.) If only one tiny little light is lit on your screen at any given moment, give 2 reasons why do we perceive that the whole screen is lit at all times.

4.) Explain screen resolution and how it effects the image on your screen.

5.) How is it that we seem to see all the colours of the rainbow on a screen when there are only 3 colours projected?

6.) What are 3 things could happen to your picture when you display a 4 x 3 image on a wide screen TV ?

7.) If you saw the movie "White noise", you know that what most of us call "snow" ( relating to the TV picture ) is supposed to be called noise. How does the ratio of signal to noise affect your picture?

8.) How many decibels is an example of a signal-to-noise ratio of a good video camera, and one of really poor signal-to-noise ratio?

9.) Explain codecs?

10.)  Why are “talking heads” most of what you see on TV?