CRT vs LCD

[Dark Jaguar]

I've read a lot about the nature of each screen and it seems CRT still has some advantages, but one that I can't quite understand seems to be the lack of a "native resolution" in CRT moniters.

Why don't CRT moniters have a fixed resolution? The phosphors and pixels are fixed in place physically aren't they? That is, that red phospor patch is always RIGHT there and can't be shifted left and right, so why is it that they don't have a locked native resolution?

 

[Dark Jaguar]

Blast, I just realized I posted this in the wrong thread. Feel free to move it to the tech thread. Sorry!

 

[epepke]

Why don't CRT moniters have a fixed resolution? The phosphors and pixels are fixed in place physically aren't they? That is, that red phospor patch is always RIGHT there and can't be shifted left and right, so why is it that they don't have a locked native resolution?

No.

 

[Dark Jaguar]

Is my premise incorrect? Do CRT moniters have a native resolution after all? My sources must be flawed then.

http://en.wikipedia.org/wiki/Native_resolution

This and a lot of reading on my part regarding LCD screens, CRT screens, and the tech responsible for each seem to indicate that while an LCD screen has a native resolution that makes it hard to scale anything that isn't perfectly divisible into that native resolution (without artifacts anyway), CRTs do not in fact have that issue. I am just not clear on why. If the articles are incorrect, please explain this too.

"No" just isn't sufficient .

 

[casebro]

I think I agree with you. You did post it in the wrong place.

But also, good question. I know LCDs are brighter, but don't have the resolution- the pixels are too big. My guess is that all those options for resolution on a CRT are fantasy. But to do the same on a LCD would show artifacts of the larger pixels.

 

[TPrime]

The way I understand it, there are no "pixels" in a CRT. The inside of the front glass is coated with something that responds to an electron beam, and that beam can be adjusted to hit a larger or smaller region.

 

[Janus]

CRTs are analog devices. The surface of the display is only broken up in to a discreet grid because thats the most useful way for the computer to drive the display. It might be useful to think of it like a film camera. The graininess of the film imposes a upper limit on the finesse of details that be captured but apart from that it will reproduce whatever passes through the lens. In a CRT its the graininess of the shadow mask and the responsiveness of the electronics that determine the upper limit. The lower limit is also dictated by the electronics (they still have to synchronize with the input signal) but also if the image is too sparse then the black gaps between the scans of the beam will be too visible.

 

[Dark Jaguar]

Except that on a color CRT screen (which is what I normally think of when I think of CRT) each phosphor "packet" or whatever unit releases a specific wave length of light. So no matter what you do with the electron beam, if you can get one to hit that particular phosphor blob, it will ALWAYS emit red light, and so on.

So my question is, doesn't that put a built in upper limit on the resolution based entirely on the size of the red blue and green phosphors on the screen? Is the size basically just at the ridiculously small point compaired to pixel size?

 

[a_unique_person]

They will run in any resolution, but in the non-native resolution will look blurry.

 

[Janus]

So my question is, doesn't that put a built in upper limit on the resolution based entirely on the size of the red blue and green phosphors on the screen? Is the size basically just at the ridiculously small point compaired to pixel size?

Yes, but the image will have degraded in quality before that limit is reached. The stream from the electron gun doesn't target individual dots and there are limits on how fast the gun changes intensity. The result would be that the pixels begin to merge into each other before the granularity of the phosphors is reached.

 

[Dark Jaguar]

So I guess my final question is, any exact numbers on how granulated the average CRT (standard NCSC format TV) screen is? I'm basically expecting a ridiculously huge number from what I'm hearing here.

Essentially, the granularity on a moniter is far and away above the granularity (individual pixels) of an LCD screen. Is that it? Now it makes sense to me, as well as why I can pan and resize my moniter's image (though I would prefer a preset for every possible resolution to automatically reach "to the edge").

Thanks for the help. Now then, any way to solve the issues with LCD screen's limitations, outside of making a very very small pixel?

 

[Janus]

So I guess my final question is, any exact numbers on how granulated the average CRT (standard NCSC format TV) screen is? I'm basically expecting a ridiculously huge number from what I'm hearing here.

Essentially, the granularity on a moniter is far and away above the granularity (individual pixels) of an LCD screen. Is that it? Now it makes sense to me, as well as why I can pan and resize my moniter's image (though I would prefer a preset for every possible resolution to automatically reach "to the edge").

This explains it better than I can. Doing some quick maths from my own monitor I found it’s not quite as dramatic as I expected it to be. It might be misleading as phosphor elements aren’t laid out in a rectangular grid in most monitors.

Thanks for the help. Now then, any way to solve the issues with LCD screen's limitations, outside of making a very very small pixel?

Not really. You can fake it with sampling but good sampling is computationally expensive and the result is an approximation that doesn’t truly eliminate the problem.

 

[infornography]

I guess if I tried really hard I could tell the difference between resolution settings on my LCD screens, but normally, I really can't. Its not that big of a difference anymore.

Early screens did have severe problems, even as recent as 3 or 4 years ago, but on newer ones, the problem isn't nearly as noticable.

 

[Dark Jaguar]

I like the word sub pixel. Thanks for that. And apature grills line up the phosphors as solid lines of color so there's no vertical dot pitch to be seen. That's also interesting to note.

 

[Art Vandelay]

CRTs are analog devices. The surface of the display is only broken up in to a discreet grid because thats the most useful way for the computer to drive the display.

But it's that way for TVs, too. And in this context, it's spelled "discrete".

 

[Janus]

But it's that way for TVs, too. And in this context, it's spelled "discrete".

Kinda. Traditional TV signals have discrete lines but no well defined colums. And in the context of internet forums, spellings overrated.

 

[Art Vandelay]

Well, mine is "brick wall" tiling, except rotated 90 degrees, so there are well defined columns, but not rows. And it's not merely spelling; "discrete" and "discreet" are two discrete words.

 

[jj]

Look for the term "pitch" in CRT monitors. It's the distance between holes in the shadow mask. Unfortunately, it would be nice if they were always measured the same way.

http://www.tomshardware.com/2002/03/19/comparison/index.html is a good place to start.

The video amps in a CRT are what controls the resolution in a very real way. On an LCD, the pixels are defined. On a CRT, each pixel can be several sets of phosphor dots. The rate at which the video amps can turn the electron beam(s) on and off is as important as the size/number of the dots.

I realize this answer isn't quite definitive. The comparison is not simple. It is not correct to say that a color CRT is an "analog" device, either, because the surface is sampled by tricolor dots. It has to be. Well, unless it's a Trinitron, in which case they are stripes...

 

[epepke]

Except that on a color CRT screen (which is what I normally think of when I think of CRT) each phosphor "packet" or whatever unit releases a specific wave length of light. So no matter what you do with the electron beam, if you can get one to hit that particular phosphor blob, it will ALWAYS emit red light, and so on.

The CRT mask and the distribution of phosphor dots is much finer than the highest possible resolution of the monitor. The gun will always shoot on several dots of the same color. If the gun only shot one dot of phosphor, you'd get very bad aliasing.

 

[Meffy]

Just so. It can be revealing to view various finely hatched or dotted patterns on a CRT. At high display resolutions, white dot patterns on black often show a lot of color aliasing.