Why does CRT use dot pitch but not a LCD or plasma

Also why does CRT use hertz but not computer LCD only TV LCD?The higher the hertz less ghosting or blurr with fast moving images.But computer LCD use response time in nanoseconds but not CRT .

Why does TV LCD use response time and hertz but not computer LCD.And why does plasma or LED have no response time or hertz?

 

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Its just how they work.

A CRT or Cathode ray tube use an electron beam fired at a phosphor coated piece of glass to create colours, the beam has to be fired at three different coloured parts known as the dots RGB "red green blue" the dot pitch is the distance between these dots,a smaller dot pitch is usually better but can cause clarity problems as the colours get squished together and the electron beam has trouble hitting the smaller target.

The refresh rate is the speed at which the electron gun can scan the whole screen from one corner to the opposite per second,75hz = 75 screen scans per second,the faster the electron gun can scan the smoother the picture will be but the faster it scans the less time the electron gun will hover over each dot so the display will also get dimmer.

The quality of the screen therefore is judged on how close together dots of the same colour are are,the resolution which is the number of pixels per area of screen and how fast the electron gun can move across the screen and still provide a bright vivid picture.

An LCD doesn't work like this,it uses a liquid crystals of different shapes to polarize light or only allow certain wave lengths of light through which produce different colours but it doesn't emit any light so a back light has to be position behind the screen for you to see the colour.The only difference between LED and LCD screens is that the backlight in an LED is a Light emitting diode or LED.

The quality of the screen therefore is similar to a CRT's dot pitch but each dot can produce the full range of colour so the only number that matters is the resolution,pixels per screen area.Because it doesn't use an electron gun that scans the screen there isn't a refresh rate as such so the number that's important is the speed a pixel can go from black to white and back to black,response time.

BUT refresh rate is also sometimes used with regard to LCD's,different manufactures use different method to measure the refresh rate of screens but basically its the number of times the whole screen is calculated and re drawn by the display.It is an important number as even if your output format 'a movie for instance' only displays 24 'frames per second or frame rate' the screen can insert electronically generated mid image an image halfway between these two which will make the video appear smoother,this isn't needed when its a computer display as the output image from computer is refreshed at the same speed as the screen which is usually faster than the human eye can detect and why only the response time is usually quoted,some manufactures also use refresh rate in LCD's and LED's to denote the speed at which the back light flickers on and off.

Plasma screens work like CRT's,they have three little colours bulbs again red green blue very close together but the standard specification for how close these are is not dot pitch its known as pixel pitch but its the same thing.The problem with having a smaller pixel pitch isn't due to how accurately an electron gun can hit it in a plasma but it still affects the clarity of the image,different manufacturers use different methods to measure the pixel pitch.

I hope that's answered your questions

 

That is arguably the best explanation I have read to date and worthy of at least 2-3 re-reads.

Does:

The "distance" of the "projecting" device (gun, globe, light output from the glass (output surface of any generic composition) figure into quality? Also considering gas composition and density. In other words distance can increase the amount of particles hitting a specific "point" (pixel) till we hit the top of the curve, vacuum/gas composition optimises (will help) the transfer of light (particles in general) maximising density.

 

There's one thing I want to add to my post to eliminate confusion.

I stated that 'the resolution is the number of pixels per screen area' which is wrong,the resolution is simply the horizontal number of pixels multiplied by the vertical number of pixels,the size of the screen area or size of the screen isn't taken into consideration.

That's what pixel pitch is for,the pixel pitch is the area of the screen divided by the number of pixels.

 

I think what is confusing is when you go to store to get computer LCD they talk in response time and when you go to store to get a TV LCD or TV LED they talk in response time and herz.But any computer book does not talk about herz when looking at LCD other than response time.

Go to a store to get some LCD TV they have 120 or 220 hertz.That is what is confusing .


What determines the sharpness and brightness?

 

Brightness is determined by the power of the backlight you can't just turn the brightness up though as the blacks become washed,so the brightness is really determined by the quality of the panel.

Sharpness is the clarity of the picture,turn the sharpness down and picture becomes more blurry,turn the sharpness up and you can see the noise in the signal,find a balance.

 

What do they call this in the store?

How many pixels per screen ?

 

No pixels per screen is pixel pitch,sharpness is digital noise cancellation.

If the broadcast is a fuzzy signal and you turn the sharpness down the picture will become more blurred but look better,if you turn the sharpness up the picture will become clear but you will then see small mistakes in the signal which will cause it the picture to look bad.

∴ The key is finding a balance. EDIT Danielson.

 

I got it pixel pitch the higher the better.


Also most all LCD monitors have same brightness around 300 from what people say.Well plasma and LED can show more color than LCD and is also much brigher .