CurtPalme.com Home Theater Forum

[deronmoped]

Flickering of the display and sharpness.

Lower refresh rates and how it's perceived by each individual person can cause this to be a issue.

Now this got me to thinking. Flickering is from the image not being displayed, kinda like a strobe light effect. Now for a display to achieve this effect, it needs to be off for a certain amount of time. This now relates to running lower refresh rates to: 1) get a sharper image 2) to reduce the load on the displays electronics. But is that totally true? Surely it would reduce the load on the electronics, one way or another. That is, slowing down the rate at which it has to draw the image, or resting between drawing of images.

Now is there a "low" speed limit on how fast a display will draw a image, not going below that rate of speed. It would seem to have to be, because if it did draw the image, just at a slower and slower rate, there would be no flicker, or the flicker would not be so apparent. The more apparent the flicker the more pronounced the contrast has to be between bright and dark. If there is always light being displayed, there is no flicker, or as much flicker that would be produced if the image wasn't there at all.

Now how this applies to how lower refresh rates effect how sharp a image is. It seems that if a display does not go below a certain speed when it draws the image, then lowering the refresh rate below that speed will not help with sharpness. Just add to flicker.

Now this is my best guess at what is going on, what do you guys think?

[gjaky]

I don't think the sharpness is directly affected by refresh rate, but only through the bandwidth limitation of our machines (so you can get sharper picture at 1080P-60Hz than in 1080P-72Hz, but 800x600-60Hz wont be sharper than 800x600-100Hz on a mid level machine)
The phosphor has a persistance, they emitt light even after they were excited by the electron beam, the persistance varies by the type and color of the phosphor (note: the P43 fast green has lower persistance than the standard green we use).
The flicker sensitivity also varies to every people, some are more sensitive some are less, but a general rule that the peripheral vision is more sensitive to flicker than the foveal vision, so the bigger the viewing angle the more you notice the flicker.
From electronics side there would be no reason to limit the minimal refresh, but they do this yet to prevent the possibility of spotburning the tubes, and the low refresh would flicker like crazy anyway. See: http://en.wikipedia.org/wiki/Flicker_fusion_threshold

[CasetheCorvetteman]

Just cause your machine is drawing the image slower doesn't mean it draws any one spot as often, lower refresh means longer time prior to next pass, more time for phosphor to return to dark. You see the flicker when the time to next pass exceeds the time taken for the phosphor decay, it goes dark quick enough for you to see it is darker, before being re-lit.