Seeing through the computer
The sense of vision is a very important if not the most vital of all the senses we possess. This is the reason why it may be very hard to imagine trying to use your computer without the aid of visual feedback that you receive across the screen of your monitor. But do you know how the images that you see in your computer monitor are compiled? We will focus our discussion on how colour images are displayed on your computer screen.

Primary colours
At the very basic level, you need to understand that when it comes to light waves, any colour in the visible spectrum can be created by combining red, green and blue in respective proportions (my kindergarten art teacher taught me that any colour can be made by combining red, yellow and blue. This is true for paints and dyes, but when it comes to light rays, the primary colours are red, green and blue; yellow is made by combining red and green).

Your computer screen is made up of thousands of tiny dots that are packed closely together and arranged as a grid. Each dot is capable of producing red, green or blue light at the pulse of an electric current.

There are many techniques that are used to produce this light; including the conventional cathode ray tubes (relatively large - TV like monitors) and flat screen monitors. Even though their inner workings are different, all of these work on the same principles to display the graphic information that you see on your computer screens.
The dots I mentioned earlier are referred to as ‘pixels’ in computer terminology and you can actually see them with your naked eyes.

The three primary colours combine in different magnitudes to give each pixel its designated colour at a given time and all the pixels in combination creates ‘the big picture’ with its different colours and tints. Each pixel can change its colour many times a second and so it is possible for the computer to ‘paint over’ many images on the screen each second.

The rate at which this ‘painting’ is done is called the ‘refresh rate’. Computers and televisions use this technique and a high refresh rate to create a seemingly smooth moving picture on the screen whereas in reality they are a sequence of still images played in rapid succession.

Refreshing images
The human eye can retain a visual image for 1/10 seconds on average, so any image sequence that changes smoothly at least 10 times each second is capable of creating the same effect as a movie. However in TVs this image changes 25 times each second making the movement seem even smoother and more realistic.

Computers also use the same technique, but the refresh rate in computers is much higher and is in the region of 60Hz and above. It is important to remember that even though you may not notice it, your eyes are sensitive to the constantly changing sequence of pictures on your computer monitor and it is recommended to use a refresh rate of 72Hz or higher to minimize the possibility of eye damage. Now you know the basic principles that the computer uses to display images on the computer screen, so we can dive deeper into how it is done in practice.

Binary vision
You already know that the computer monitor is made up of ‘thousands’ of pixels. When painting an image on the computer screen each pixel has to be designated the given colour. Computers do not understand the concept of colour, the only language they understand is that of binary ‘1’ or ‘0’. So colours are represented within the computer as sequences of ‘1’s and ‘0’s.

For example a sequence of 3 binary digits can be arranged in 8 different combinations representing 8 different colours in this instance (which is given by the formula N=2n where n is the number of binary digits and N is the resulting number of different combinations).

It is clear that by increasing the number of digits, you can effectively increase the number of colours that can be represented. The number of different colours that can be represented is called its ‘colour depth’.

When painting a picture on the computer screen, the exact colour of each pixel has to be derived from the designated binary sequence and that information has to be converted in terms of the intensity of the red, green and blue dots on the screen.
This may seem a simple task on the outset, but when you consider that about 70% of all computer screens operate at 1024 X 768 pixels on the computer screen, decoding the colour of each pixel 72 times each second is no easy task. For all practical purposes it is possible to group multiple pixels on the monitor together and treat them like one single pixel.

Resolution
This can reduce the burden considerably at the cost of valuable ‘space’ in the working area of the monitor. The total number of logical pixels on the monitor at a given time is called the ‘screen resolution’ and as mentioned earlier, the resolution of 1024 X 768 pixels is currently the most commonly used screen resolution for most computers though higher screen resolutions of 1152 X 864 pixels and lower resolutions such as 800 X 600 pixels are in use.

The screen resolution is an important factor to consider when designing application interfaces especially for software applications and websites. As mentioned, decoding all the video information is usually far too heavy a burden for the main microprocessor to handle alone.

This is why modern computers are equipped with high performance video cards that are especially designed to crunch the graphic information of the computer with more efficiency, thus reducing the burden on the processor. We will discuss the workings of video cards and different types of computer monitors in detail in the coming weeks.

Postscript
The monitor is only a tool that is used to provide you with certain information and feedback that is produced by the computer. It is not difficult to argue that sound and synthesized speech would be a better method for certain forms of output generated by the computer.

For example, pre-recorded messages would be a better alternative in place of message boxes and error notifications that we often come across in present operating systems.
Some people claim that interactive speech capability will be the defining factor of the next generation of computer operation systems.

While this has an element of truth, it still cannot undermine the importance of the visual component of the process of human - computer interaction. The average computer will need to have full multimedia capabilities right through the foreseeable future and all you need to do to clear your mind of any doubts about this is to imagine playing ‘Need for Speed’ without your computer monitor (or VR goggles). While it is undisputed that the visual component of human-computer interaction will always be very important, where do we go from here? Let’s face it; computer monitors (and even TV sets) have become outdated.

What about 3D visual displays for PCs? When do we leave the unexciting two dimensional world of our high-tech flat screen monitors, to experience the less virtual and more realistic world of 3D displays? The answers could be ‘out there’, in the future or they could be floating among the ideas and imagination within our own minds.

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