HDTV's


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Old 01-30-08, 06:25 AM
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HDTV's

I have been educating myself on HDTV's and I see a term called 120Hz being used. After researching, I now understand how a 120Hz HDTV is better that previous earlier refresh rates. Now, my question is this, looking at several HDTV specs, I am not finding where the 120Hz or any Hz rate is referenced. I do see where some are referencing 3:2 and 3:3 pulldown. I understand that 3:2 pull down is like a 30Hz HDTV but is the 3:3 = 120Hz? This is the only place within the HDTV specs that I am finding reference as to what the Hz is for that set. Can someone assist me.

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Old 01-30-08, 09:27 PM
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I believe most TV video sources are 60 Hz. This means the picture refreshes 60 times per second. There is progressive, or non-interlaced, which means the entire picture refreshes every 60 seconds. There is also interlaced, which means one half of the horizontal lines refresh on a cycle, then the next half on the next cycle, giving you 30 FPS (frames per second).

I think the pulldown refers to how the 24 FPS from film (movies) is converted to 30 FPS, or 60 fields, on TV's. 60/24=2.5. It works out that 2 frames=5 fields. So, the first movie frame is shown as 2 fields on the TV, then the second frame is shown as 3 fields on the TV, then 2, then 3, and so on.

If you had a TV that had a refresh rate of 120 Hz, that would mean you could have one frame=5 fields (this is an assumption, and I don't know if this is how it works, or if there is a player or TV that does this, but the math supports my assumption, 120/24=5). A 120 Hz rate woud work well for TV at 30 or 60 FPS also. There are plasma TV's that have refresh rates of 72 hz, so 1 frame=3 fields. I would think 3:3 would be 72 Hz.

I can't tell you if 3:3, etc. makes a big difference or not. If you're watching TV, it probably won't matter. I'm sure there are technical issues with what I have said, but I hope you get the general idea. Here's a site that helped me make sense of this: http://entertainment.howstuffworks.c...eo-format1.htm
 
 

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