G-Sync CRT?

[rabidz7]

I know one will probably never be released, but... Is it theoretically possible for a CRT to have G-Sync, or do CRTs have to be locked to one refresh rate?

 

[[X]eltic]

I see no reason why it could not theoretically be possible. But it would be practically useless on a CRT, because the amount of flickering below 60Hz would become unbearable.

 

[rabidz7]

I see no reason why it could not theoretically be possible. But it would be practically useless on a CRT, because the amount of flickering below 60Hz would become unbearable.

It could be used from 80Hz-240Hz.

 

[XoR]

even if it would be possible to wait with refresh there would be issue with fluctuating brightness level which would make this CRT G-Sync pretty useless. Combining flickering/strobing (Lightboost/ULMB) with G-Sync is hard enough and combining CRT with G-Sync would be probably order of magnitude harder...

 

[Church]

As manufacturers decided to mostly stop further develop crt in general, i see no way for spending time and money on adding functionality for something they won't produce and won't sell. Lot of things are possible theoretically, but one should be more down to earth estimating what actually makes business sense to make as real product. Or you estimate chance of making custom gsync PCB replacement boards for not anymore produced crt monitors that slowly die out due age as higher then >0.00001%?
It can be done. It will not be done. Zed is dead, baby. Zed is dead. Or spend few $100K minimum (if not few $M) for producing custom one-off crt monitor of such kind for yourself.

 

[XoR]

It can be done

no it cannot because of brightness issues. It would be impossible to regulate brightness to avoid visible brightness fluctuation because it can only be done by regulating voltage and pixel brightness response to voltage (gamma) is not linear nor any simple function. It is close to power function but not quite. To make things worse this function change over monitor lifetime so its kinda hopeless..

With LED backlit LCDs and OLEDs you can use PWM that is much more linear and hence it might be actually possible to have brightness of frame reverse proportional to frame rendering time (eg. very bright for very short frame times). It would still be prone to flickering at lower framerate, probably even made people sick just out of pure fluctuating flickering even if overall perceived brightness would be the same. On CRTs however its just physically impossible to avoid brightness fluctuation so it would definitely made people sick. Not to mention that we do not really know if it would be possible to have such variable frame-times in the first place or if it maybe was possible but there were issues with geometry, etc.

you cannot assume that everything is technically possible...

 

[sharknice]

no it cannot because of brightness issues. It would be impossible to regulate brightness to avoid visible brightness fluctuation because it can only be done by regulating voltage and pixel brightness response to voltage (gamma) is not linear nor any simple function. It is close to power function but not quite. To make things worse this function change over monitor lifetime so its kinda hopeless..

With LED backlit LCDs and OLEDs you can use PWM that is much more linear and hence it might be actually possible to have brightness of frame reverse proportional to frame rendering time (eg. very bright for very short frame times). It would still be prone to flickering at lower framerate, probably even made people sick just out of pure fluctuating flickering even if overall perceived brightness would be the same. On CRTs however its just physically impossible to avoid brightness fluctuation so it would definitely made people sick. Not to mention that we do not really know if it would be possible to have such variable frame-times in the first place or if it maybe was possible but there were issues with geometry, etc.

you cannot assume that everything is technically possible...

If you limit yourself to how current CRTs work you can't, but if you add technology to them you could do it. I'm sure someone could find a way to manipulate it somehow to adjust the decay time on the fly, through the screen or the the gun. For example you could add some sort of filter on the screen that adjusts the brightness according to the time between frames.

GSYNC CRT is never going to happen though. CRTs are basically a dead technology.

 

[XoR]

pehaps you do not have faintest idea how CRT work...
for starters watch this educating movie: https://www.youtube.com/watch?v=lRidfW_l4vs

LCD refresh their pixels state in the same fashion but with G-Sync you do it always in 6.9ms (1000ms / 144) and can afford to wait almost howerer you want for next frame cause liquid crystals retain their state for quite some time and your light source is completely independent. With CRT you have gun sweeping screen. If you draw screen always with the same speed but regulate blanking times then you hit brightness fluctuating issues. You could also redraw screen with different speed depending on frame rendering time but that would require you to either add input lag or draw at eg. half frame time (to get lag-less range from eg. 72 to 144Hz). Issues with fluctuating geometry would most probably occur there and brigthness would still fluctuate. Obsiously serious redoing of electronics would be needed...

But that is kinda academic discussion. We do not even have G-Sync with flickering on LED LCDs where it is actually easy and straightforward thing to do with just some simple modification in firmware... in theory at least... and as practice show there is always more issues where we anticipate them to be

 

[sharknice]

pehaps you do not have faintest idea how CRT work...
for starters watch this educating movie: https://www.youtube.com/watch?v=lRidfW_l4vs

LCD refresh their pixels state in the same fashion but with G-Sync you do it always in 6.9ms (1000ms / 144) and can afford to wait almost howerer you want for next frame cause liquid crystals retain their state for quite some time and your light source is completely independent. With CRT you have gun sweeping screen. If you draw screen always with the same speed but regulate blanking times then you hit brightness fluctuating issues. You could also redraw screen with different speed depending on frame rendering time but that would require you to either add input lag or draw at eg. half frame time (to get lag-less range from eg. 72 to 144Hz). Issues with fluctuating geometry would most probably occur there and brigthness would still fluctuate. Obsiously serious redoing of electronics would be needed...

But that is kinda academic discussion. We do not even have G-Sync with flickering on LED LCDs where it is actually easy and straightforward thing to do with just some simple modification in firmware... in theory at least... and as practice show there is always more issues where we anticipate them to be

I understand exactly how they work. Did you even read what I posted?

 

[SH1]

Fortunately, CRTs already look great, 'cause this ain't happening...maybe OLED?

 

[flod]

If you limit yourself to how current CRTs work you can't, but if you add technology to them you could do it. I'm sure someone could find a way to manipulate it somehow to adjust the decay time on the fly,

rate of decay is determined by physical properties of the phosphor. and even if you decrease the rate of decay, that doesnt imply increased luminance over a single frame, which is what's needed to have gsync not appear flickery when framerate changes.

though it's definitely a very difficult/impossible problem to have gsync on crts, it's worth thinking about as eventually we'd like to have gsync on rolling-scan oleds

 

[sharknice]

rate of decay is determined by physical properties of the phosphor. and even if you decrease the rate of decay, that doesnt imply increased luminance over a single frame, which is what's needed to have gsync not appear flickery when framerate changes.

though it's definitely a very difficult/impossible problem to have gsync on crts, it's worth thinking about as eventually we'd like to have gsync on rolling-scan oleds

Yes. You could do it if you came up with a way to modify the phosphor, use a different phosphor, or add a filter in front of the screen that can dim or amplify the brightness.

For OLED I think it would be much easier because you can already control how long a pixel persists with existing technology.