CurtPalme.com Home Theater Forum

[km987654]

What is the point in more vertical frequency. Say going from 155hz to 200hz or beyond??

[ecrabb]

Refresh? Who runs refreshes like that? Where have you even heard of it?

The only groups that run really high refreshes are people doing immersive 3D where they need double refresh for active stereo LCD shutter glasses, and gamers on desktop CRT's, but neither of those groups run beyond 100-120hz as far as I'm aware. I've never heard of anybody running a 155-200hz refresh or beyond.

Are you sure you're not thinking of bandwidth? Signal bandwidth for a high resolution and refresh can easily run up into the 200+mhz range.

SC

[tse]

Motion would be smoother with that many different frames.

Scott

[ecrabb]

Motion surely would be super-smooth at those kids of refresh rates - assuming you had a source that would support it (real-time 2D and 3D as in VR or gaming)... But, no normal consumer video sources could take advantage of it. 1080p @ 72 or 75 hz is the highest practical signal we need for HT.

I wonder how many displays outside of a super specialized commercial market would even support refreshes like that at any but the lowest resolutions. I know there are some graphics-grade CRT monitors that will handle 120hz or higher refresh, but they would only do it at lower resolutions like VGA or SVGA. As soon as you got up into the 1600x1200 range, then you were limited to 60-75hz.

1080p at 120hz would require somewhere around 375mhz worth of bandwidth, wouldn't it?

SC

[perisoft]

The eye can't see better than about 60fps in the best of times (very bright light). In dimmer light your effective motion perception ability is around 30fps. If you could actually see the difference between 150fps and 100fps, 24fps movies would look like a bunch of photographs. Gamers try to run huge refresh rates, but it's placebo; nothing more. And even if the eye could perceive the difference, it would be meaningless on CRT front projectors, since the phosphor decay time is even longer than on standard CRT monitors. If you're not seeing flicker on a CRT, either the display device or your eyes aren't quick enough to notice any frames stuck in the middle anyway.

And, yes, with movies / video you have a 24fps source, or maybe a 60fps source for HD material (not sure about that). You could run 6000hz but you'd just see the same frame a hundred times in a row. Yes, technically you could interpolate the frames, but that's very intensive and would be pointless for the above-mentioned reasons.

[ecrabb]

But, 24fps DOES look like a bunch of photographs sometimes - especially with large/high-contrast areas and a fast motion. Besides, the flicker at 24fps is hideous, which is why projectors use a 3-bladed shutter. Even with 72 short flickers per second, flicker is still noticeable - especially in your peripheral vision. Of course, shutter flicker is a worst-case scenario. My point for mentioning the projectors was just to point out that flicker in film projectors is very short-duration instances of no light at 72hz, and it's certainly not invisible. That implies to me that the motion sensitivity goes well beyond 60hz.

Now, you might be right that there wouldn't be a huge difference between 100fps and 150fps, but I suspect that either would look VERY different from 60fps. I suspect the vision mechanism is probably much more sensitive than you think it is. Can you point to some research that shows the eye's upper limit of motion/flicker sensitivity tops out at 60hz? I did a quick Google, but didn't see anything pop up immediately.

Yes, 720p has a 60hz capture/display rate. 1080i is 60 fields/30 interlaced frames per second.

SC

[perisoft]

ecrabb, I dug that up doing research for my "Light, Color, and Vision" class in college. Probably the only thing that was interesting the whole time. And that was pre-wikipedia - all scholarly sources. No f*cking clue what they were, though.

[Person99]

[perisoft]

It would be interesting to do a frame-interpolator for 24 frame stuff. At that level, going to 48hz would make a significant difference in some scenes (long, steady pans always bother me if it's a bright image). It's tricky software at best, though, and it would definitely have to buffer material to preprocess, which would be a real pain in the ass.

You could do it, though. Would be an interesting project, but you'd have to sell 'em for ten grand even if you wrote off your time.

[Person99]

[km987654]

I am reading the Barco reference sheets for the data and graphics models. Most have vertical scan rates of 37-155 but others scan to 200hz or better. So what benefit is there for HDTV in going from 155hz to 200 or more? RGB bandwidth is another matter.

[AnalogRocks]

[AnalogRocks]

[Person99]

[MikeEby]

[AnalogRocks]

It does look very odd. Almost like the old day's when you were watching a TV show shot on film and they ended up shooting one scene on video tape. The picture just wasn't right.

[AnalogRocks]

It does look very odd. Almost like the old day's when you were watching a TV show shot on film and they ended up shooting one scene on video tape. The picture just wasn't right.

[km987654]

My first post says "vertical frequency" as per the Barco cross reference tables. As stated most are at 37-155 but some are at 200hz or better.

As I understand vertical frequency is measured in Hz and horizontal frequency is measured in Khz.

[WanMan]

[Dave Lister]

[Person99]

[MikeEby]