This post was one of the first posts published, under a different title, on this blog back in 2008. It has been rewritten since first publication.

I love CRTs – Fact.

Why?

• Is it because they heat my room and give the central heating a rest? No.
• Is it because they allow me to fill space that would otherwise be used for unnecessary items? No.
• Is it because they trap and attract dust, lightening my workload with the duster? No
• Is it because they consume more power and assist me to help my chosen electricity company to increase its’ profits? No.

The reason is that there is no picture equal to a CRT picture. – That is a fact.

There is no comparable picture from any flat-screen TFT (Thin Film Transistor (Or LED(Light-Emitting Diode – which is basically a simple transistor with an unconnected collector.))) monitor ever built which is able to rival the uniqueness and completeness of the picture on an old CRT (Cathode Ray Tube) monitor.

I fondly remember this CRT monitor that I was using when this article was originally written in 2008. It was manufactured in December 1999 and lasted until July 2010. Its picture was excellent. : R.I.P. old friend. – It appears that your species is almost extinct already.

The cathode ray tube is exactly what it says on the tin: Basically it’s a tube which has one widened out end with a screen on it, with a special thermionic valve at the other end, known as an electron gun, producing three rays of electrons. These electron-rays are propelled along the tube from the valve end, electromagnetically steered by the frame and line coils attached externally around the thin neck of the tube – which you normally don’t get to see from the outside of the monitor, and sequentially targeted onto one of many groups of three different tiny dots of reactive phosphor on the inside of the screen; producing light with either a red, green, or blue wavelength.

Red, blue, and green are the three primary colours from which all other colours are made up: Yellow, for instance, is just an intense green. White is a mixture of all three colours at a high-intensity in almost equal proportion to one another.

Each cluster of three phosphor dots is being hit by all three electron beams, one beam hitting each dot, many times a second, in a process known as scanning: The electromagnetic coils affixed to the tube inside the monitor steer the electron beams to hit the first set of dots; the “red” beam always hits the “red” dot; which is made of a phosphor which emits red light when it is hit by an electron beam, and likewise with the “green” and “blue” beams. (The beams themselves have no colour as such; in fact they’re to all intents and purposes invisible. They travel as minutely thin particle-beams within the vacuum <Vacuum meaning lack of air molecules that is, not a Hoover.> inside the tube until they strike a phosphor dot on the screen, producing light accordingly.)

After hitting the first cluster of dots the beam is fired at the second set of dots…and so on. This process happens at incredible speed; so fast in fact that the human eye doesn’t perceive it, but rather sees a complete picture.

After the entire screen has been covered and all the clusters have been hit the process happens again. The number of times per second this process happens is the screen’s “refresh rate”, and is controlled from the computer’s graphics chip, with a relevant GUI (Graphical User Interface) in Windows operating the chip’s settings by means of Direct X -Which provides an interface between the Windows operating system itself and the components of the computer. (As in – ‘the graphics card’… You get my meaning? – ‘Sorry to be rather obtuse. :S )

(If you use a CRT monitor and the screen appears to flicker; try setting the refresh rate frequency to at least 80 Hz: Anything less tends to cause eye-strain from a CRT monitor.)

So that’s very roughly how it works; but why does it produce a better picture? The gun electrodes of each of the sections of the valve producing the three electron-rays can have their electrical potential varied by the monitor’s analogue circuitry extremely precisely, more easily, and faster, than each individual transistor in a TFT monitor. Since the electrical potential of a single trinity of cathodes in an electron gun affects the entire picture in a CRT, rather than each individual transistor’s electrical potential, as in a TFT, this negates the relevant circuitry’s function at such a high speed in order to give an exact blend of colour true to the analogue input waveform in the case of a CRT, thus giving less chance of error due to lack of responsiveness of given components: For instance if the first, third, fifth… cluster required a bright pixel and the second, fourth, sixth… cluster was required to be a dim pixel, a CRT monitor would simply increase the voltage on the gun-anode as the electron beams fired at the first cluster, then decrease the gun-anode’s voltage on the second cluster, and so on… A TFT monitor, however, first has to digitally address the first set of transistors corresponding to the first pixel and increase their voltage, then digitally address the second set of transistors corresponding to the second pixel and decrease their voltage…and so on: Therefore the digital circuitry in the TFT monitor has to work many times faster than the analogue circuitry on the CRT monitor. Quite obviously technology has found a way around this problem to a certain extent by using complex algorithms and digital matrices, as well as the increased switching frequencies of individual transistors on a silicon wafer; but still overall are better and can reproduce better and more colours as a result.

Another way of putting it would be that the cathode rays fired from a CRT monitor’s electron gun are an amplified and processed analogue representation of the monitor’s original input signal, as in a way is the CRT picture itself. A TFT or LED monitor, on the other hand, either accepts a signal that has been digitised or is digital; or it has to digitise an analogue signal that it receives; thus losing some of the information originally contained in the analogue waveform as it does so.

- So that’s the technical bit covered very basically, although not at all thoroughly: It gives you a very rough idea of what’s going on. The real conundrum, however, is in relation to the human eye and the claimed colour reproduction statistics of TFT vs. CRT monitors: According to statistics; a decent TFT monitor is capable of accurately reproducing 24 million colours; whereas a CRT monitor is capable of accurately reproducing 32 million colours. Seeing as the human eye, according to scientists, is only capable of perceiving 24 million colours, it should follow that a CRT monitor, by all logic, should appear to give no better picture than a TFT monitor. However this is clearly not the case; therefore someone somewhere appears to be cooking the books; as the figures just don’t add up.

- Ok, so not accounting for the extra space required to accommodate a CRT monitor on my desk, the extra heat generated by the high-voltage circuitry inside – as well as the electron gun’s heater element (which makes the thin end glow a bit and get hot), and the extra electricity consumed beyond the requirements of its TFT counterpart, a CRT monitor otherwise is better. – ‘Just that they don’t make them any more, they’re hard to get hold of, and I’ve only got 1 left. – Yes I’m actually looking at a CRT monitor’s screen while I’m editing this. – When this CRT monitor bites the dust I will replace it with a TFT/LED monitor, of which I currently have 2 spare. Until then I will continue to watch my computer’s visual output on this rather old CRT monitor with the branding “AOC  Spectrum 5Glr” written below the screen. <Yes it IS a wonder that it’s still working.>