Panasonic: 480 Hz sub-field refresh - Canadian TV, Computing and Home Theatre Forums
 
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post #1 of 6 (permalink) Old 2008-11-26, 03:34 PM Thread Starter
 
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Panasonic: 480 Hz sub-field refresh

This seems to be a big point in the adds I see for Panasonic Plasma TVs. I've been trying to figure out exactly what this means.

I've found various conflicting explanations on the web but very little in the way of consensus. Are there any experts on the forum that can explain what this means. In particular I'd like to know what they mean by a sub-field. Is it a smaller rectangular portion of the display? Is it a field made up of every other 8th scan line? Is it a full frame field rendered at a faster display rate? Or something else entirely?

I gather that most plasmas have had something like this for a long time and it's just now that the marketers are starting to put it into adds so these plasmas can sound better than the "120 Hz" LCD.

Finally: more to the point - does it have any visible effect (say compared to the claimed 840 Hz of the Pioneer Kuros)?
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post #2 of 6 (permalink) Old 2008-11-26, 06:27 PM
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Each "pixel" on a plasma is actually made up of 3 sub-pixels, one each for R,G,B. The way a plasma changes the intensity of the light output is to rapidly turn on/off (aka modulate) the individual sub-pixels.

As you can imagine for a 60Hz signal they have to modulate it much faster than that rate to make the picture look good.

In theory the faster the modulation the better since it should allow you to display finer gradations in intensity.
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post #3 of 6 (permalink) Old 2008-12-15, 09:41 PM
 
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Panasonic Plasma uses 8 subfields to make up a single video frame. In fact Panasonic plasmas have always used 8 subfields. Even from the old days of Plasmaco. There is nothing new here. The number 480Hz came about as a just a marketing ploy to compete with LCD 120Hz.

They got it by the following math:

8 subfields per frame x 60 frames per second = 480 subfields per second = 480Hz

If Pioneer were to stoop this low they could claim 840Hz since they use 14 subfields
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post #4 of 6 (permalink) Old 2008-12-16, 06:49 PM Thread Starter
 
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I'm still curious about what exactly a subfield is. Is it a full frame displayed 8 times, or is the frame divided into spatial subframes.

The other question is: is faster subfield refresh better, and can you actually see the difference.

BTW: last week I bought the Pioneer 5020 Kuro based on a side-by-side comparison with a Pana PZ800 and a Pana PZ80. In a darkened room the Pana's seemed to glow on a "dark" frame, while the Pioneer was very dark. The colour gamut of the Pioneer also seems much better. Watching the "Planet Earth" blu-ray disks is truly mind blowing! Watching these you get a very palpable sense of 3D realism.

If these differences are due to the Pioneer's faster subfield refresh ... it certainly seems to work! The Pioneer's display is truely amazing!
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post #5 of 6 (permalink) Old 2008-12-16, 06:58 PM
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The sub-field is probably referring to the ability to modulate sub-pixels individually.

A single pixel is made out of three sub-pixels, one each for R, G, B.

As for the glow, the Kuros are the best in the game for absolute black level.
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post #6 of 6 (permalink) Old 2008-12-16, 07:32 PM
 
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Plasma displays do not modulate light with voltage like an LCD does. There is only one light intensity and to create gray scale the panel must use a form of pulse-width-modulation using subfields.

A subfield is an alotted time period to emit light within a frame period. These time periods are weighted either in a binary scheme or contiguous.

For example, Panasonic uses Binary I believe. Therefore there are 8 weighted time periods to emit light per frame.

1
2
4
8
16
32
64
128

The panel then can selectively use combinations of these subfields to create 256 gray levels per sub-pixel (R,G,B)

As for black level, it would take 5 pages to properly explain but in short Pioneer is king thanks to the use of CLEAR driving in combination with a very high gamma electron emitting layer on both the phosphor and sustain electrodes. This makes it very easy to reset and prime the pixels with very little unwanted light emission
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