Why do we need 120hz for watching 3d films?

[tepescovir]

Lo.
i understand why 3d monitors are supposed to be 120hz, so you can get 60 fps per eye. but why can we use a normal 60 hz lcd for watching 3d films as film is normally 24 fps, so only needs 48 frames a second. and i know my pc monitors and my lcd projector will do 48hz,
So if i'm using a htpc and 3d stereoscopic glasses to watch a 3d film, why wouldnt it work?

[Skid]

There are a number of 3D systems out there atm, the one your thinking of is the one Nvidia use, it works with shutter glasses. The idea is the 120hz is used to display alternateding left and right eye views, the shutter glasses sync themselves with the graphics cards and the monitors and close shutters over each eye when the left or right view is displayed. That make sence?

You can't use a 60hz monitor because the refreshrate of the monitor / tv is nothing to do with the FPS being displayed, most monitors can't display at rates below 55hz, and a good number of games run at 60FPS. Also while 1080p normal plays at 30 or 25 FPS, 720p can play at 60.

[tepescovir]

But most modern lcd tv's or projectors can do 48 hz, and it is a valid refresh rate on my htpc,on both my projector and tv,even fraps confirms that its 48. and a lot of others can do 1080p@50,So it should be possible to play 3d films using shutter glasses. it should simply need the software to do it for playing films

[Skid]

http://www.tomshardware.co.uk/3d-polarized-projector,review-31849.html

[Dem Pyros]

http://www.tomshardware.co.uk/3d-polarized-projector,review-31849.html

FTA:

Alternate-frame sequencing is the method of 3D realization that we used in 2007 when we put together the "Wall-Sized 3D Displays: The Ultimate Gaming Room" article. Back then, 120 Hz projectors were practically unheard of, so we settled for an 80 Hz DLP projector. This projector could display 80 FPS, delivering 40 frames for each eye. While 40 frames per eye aren’t bad, at the slower shutter speed, the strobe effect is far more pronounced. This strobe effect can make it hard to watch a 3D display for long periods of time and may cause disorientation and headaches. The issue was more acceptable three years ago when intrepid early-adopters were pioneering wall-sized 3D viewing, but it wouldn't cut it in today's mass market. It's 2010 and we expect more.

I was wondering about the OP's question myself. I'll take his word for it, though it would be nice to see an example in person to see how distracting this "strobe effect" really is.

[ChainSOV]

its probably close to an old CRT running at 40 Hz

[BHawthorne]

This is a question I wouldn't mind knowing the answer too also. I'd like to be able to do 3DVS on my 85hz projectors but nVidia locks out anything less than 120hz I guess. I also hear people mention 100hz for 3DVS? Maybe some 85hz speced projectors could be overclocked with an RivaTuner inf made for them to 100hz?

Someone needs to come out with a control box that'll modulate the shutter pulse signal to use 85hz for the 3DVS system. I'd buy that in a second just to not to have to change projectors.

[skrubol]

As mentioned above, the strobe effect would be terrible at 48Hz. I believe single projector theaters typically use 144Hz for 3d (3x24FPS per eye.)

[v3n]

Because during fast motion sequences 3D falls apart, even at 120hz it looks poor. It should really be 144hz but thats another aguement :lol: