CurtPalme.com Home Theater Forum

digitalayon · Joined: 02 Mar 2009 Posts: 394

A friend asked me this today...I had no answer.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 2252 Location: Phoenix

Hello

The v refresh must be 45 or higher; and 24 hz refresh, if you could project it, would have brutal flicker, your eye wants 48 or higher.

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Gannon · Posted: Thu Jun 07, 2012 5:06 am Post subject:

I'll second that emotion.

Was playing with a client's G90 this afternoon, and decided to try it...since it was the first with a Moome card I've toyed with since getting back in the game...and I wanted to know, too.

Brutal.

Hollywood went to 24 frames per second out of the necessity to save money on film...it was the barest minimum frame rate which would not affect the majority of people, given the brightness of the bulbs available at that time.

Nothing in our digital world requires such economy. There is actually no reason to pursue this.

Europe's TV system used 25Hz to our NTSC's 30Hz, but none of their televisions had adjustable contrast...so the peak white (or what most people call brightness) would never get high enough to trigger flicker perception. At dim light levels, the eye/brain integrates and ignores that rhythm...but for whatever reason we cannot as the overall brightness increases, or if the image is larger than our roughly 30-degree field-of-view which 'forgives' tiny motion.

The rest of our vision, out to the limits of our peripheral range, is MUCH more sensitive to even the slightest motion and flicker. This is why MOST people couldn't see DLP rainbows when they looked for them...because they trained their eyes to focus harder, which causes the eye/brain to largely ignore the periphery. Look away slightly, they couldn't be missed!

Well, as long as you don't dull your perception with continual focus upon just that wee area which integrates instead of differentiates. Like, say, with a lifetime of tiny-screen TeeVee watching! God only knows what is going to happen to a generation of SmartPhone addicts.

But, I digress. There is no need for anyone to seek to play 24fps, beyond that odd collection of Hellywood traditionalists.

As for the peripheral perception?! Tonight, I watched The Girl With The Dragon Tatoo on a rather new Sony LED-backlit LCD. The room has two doors on either sidewall, which reflected the image nearly perfectly at the center couch seat.

I kept getting distracted by very strange flashes in my periphery 'just' at the point of dramatic events and dialogue in the movie. And ONLY at those points, which could be repeated as long as I didn't try to focus upon them.

I swear it seemed to be some form of subliminal triggering. I think it bears investigation.

Same stuff would be MISSED by that 30-degree area of integration. Or ignored...or simply not noticed by our psyches, at least consciously.

But there is evidence our subconscious doesn't miss a bit.

Makes one wonder about those Hellywood traditionalists...and their desire to continue with 24p. What might they be sneaking into that space inbetween?!

Cheers,
John
somewhere north of Boulder

P.S.: I discount the hint that it might've been the LED backlighting tripping up, because it only happened during peak emotional times in the movie.

**kal** · Posted: Thu Jun 07, 2012 6:14 pm Post subject:

Most people find 48Hz flickery.

If you triple to 72Hz the flicker completely goes away but not all CRT projectors have the bandwidth to do 1080p72. Only the higher end models.

1080p72 looks identical to 1080p24. So yes, some CRT projectors can display 24Hz content. You just need to double or triple to reduce flicker. This is the same as what digitals do. Many show 24Hz content as 96Hz.

Kal

gjaky · Joined: 05 Jun 2010 Posts: 934 Location: Budapest, Hungary

Or 1080i@120Hz worth a try, it is totaly flickerless, (almost) invisible scanlines and plays 24p and 30p content as well for the bandwith of 1080p@60.

digitalayon · Joined: 02 Mar 2009 Posts: 394

but which projectors can do 1080p @ 72hz?

**ecrabb** · Posted: Thu Jun 07, 2012 8:02 pm Post subject:

**ecrabb** · Posted: Thu Jun 07, 2012 8:08 pm Post subject:

stridsvognen · Posted: Thu Jun 07, 2012 8:18 pm Post subject:

Don't forget to mention that for 1080P 72Hz you need a very good VP, and so far i didn't have luck with 1080P72hz 1.78:1 movies.

Its possible with my new Radiance XS+ and 9500LC but i cant push out the ringing in the left side of the image before my VP or projector starts to distort the picture.

AFryia · Joined: 09 Mar 2006 Posts: 740 Location: S.E. Michigan

thelasernut · Joined: 10 Jan 2007 Posts: 5 Location: London UK

"Hollywood went to 24 frames per second out of the necessity to save money on film...it was the barest minimum frame rate which would not affect the majority of people, given the brightness of the bulbs available at that time."

Flicker Rates and Frame Rates are not the same with Cine Film so there is no point in comparing 24 frame film rates with the Flicker Rates seen by a viewer.

With a Cine Projector the Film must be moved to give 24 Frames per second - its this which gives the illusion of Motion

The Projector has to hide the point where the Frame changes otherwise it would be visible to the viewer - it does this by means of a rotary Shutter which blocks the light from the projector during time that the film is moving to the next frame.

Obviously if the light was only blocked during each Frame change there would be 24 cycle Flicker - BUT - the Shutter is provided with several Blades - like a fan - so it interrupts the light several times each Frame and NOT just during Frame changes.

Depending on the number of BLADES the SHUTTER has - it follows that the ACTUAL FLICKER RATE is higher than the Film Rate and can be 48 or 72 or more times a second - So there will be NO VISIBLE FLICKER regardless of Brightness or Film Rate.

In fact this is exactly what our Displays do when they Upscale the Frame Rate to some multiple of a 24 Frame Source.

CIR Engineering · Posted: Wed Jun 13, 2012 10:53 pm Post subject:

nidi · Joined: 17 Aug 2008 Posts: 63 Location: Switzerland

http://www.youtube.com/watch?v=y1aMD6dI-rc&feature=plcp

there are 7 parts on youtube

enjoy

Michael

benareeno · Joined: 22 Mar 2006 Posts: 1463 Location: ottawa, canada

48hz on a crt has less flicker than a movie theater...people have to take some time to get used to it. But, once you do...it's great. Your immediate perception will be one of flicker...but that will change...quickly.

gjaky · Joined: 05 Jun 2010 Posts: 934 Location: Budapest, Hungary

Here in erupe the conventional tv runs at 50Hz interlaced and it's quite watchable, I don't think those two frames would make magic, however the bigger the screen the more you notice the flickering.

**ecrabb** · Posted: Sun Jun 17, 2012 8:08 pm Post subject:

Phoenixed · Joined: 13 Oct 2011 Posts: 469 Location: The mitten

Agreed Crabb. Its almost seizure inducing.

CIR Engineering · Posted: Sun Jun 17, 2012 9:08 pm Post subject:

cinema mad · Joined: 25 Nov 2009 Posts: 219

agreed,

I think when you have grown up with Pal 50 Running 48p looks fine for blu 24p & thats exactly how I run my CRT Projector but custom
1920x818 timing although I do notice the flicker some without running 48 (47.95) with custom timings ...

stridsvognen · Posted: Mon Jun 18, 2012 5:13 pm Post subject:

I grown up with 50Hz pal tv, and i get sick looking 50Hz on my CRT.. Its terrible