Plasma experts, yeah you, help me please! (experts only)

Barton Lynch · 12-03-2006, 06:21 AM

This is somewhat a re-post of my previous question on a past thread, but since I got no satisfying answer I'll ask it again. I just purchased a Panasonic 42" HDTV Plasma. I am extremely picky with PQ, almost to paranoia levels. A couple of things, first, I noticed a small level of video noise speckle on the black areas (like in the black bars of anamorphic DVDs or dark shadows in the picture, more like dancing speckling sub-pixels). This so called "faint grainy noise" is like a motion of grainy-dancing-speckles only in the very dark areas. These small dancing noise-speckles are of very dark blue and dark red and they appear -uniformly- only on the almost black and very dark hues like the darkest color gradients and deeeeeep dark grays (but not on deep blacks after a re-calibration and using the Panasonic Plasma's 'Dark' Black level setting). And they are only noticeable while looking at the screen a very close distance, one feet to be precise.

I initially thought that this was due to my very old DVD player with S-Video interface. I barely calibrated the set using commercial DVDs with the simple and plain THX setup menu (don't own Avia nor DVE, yet).

So, anyway, I finally got the DENON 'little hi-end' deck (DVD-2910) and I saw a small but perceived improvement with overall PQ using the progressive component interface. With the DENON I'm getting subtle but better saturation of colors, more natural hues, slightly sharper picture and detailed contrast compared to the very old Pioneer deck. But again this is an unfair comparison, as the Pioneer was using a composite S-Video connection and the DENON a component one (and as with the Pioneer, the de-interlacing is done but the Plasma's built-in circuity and in the case of the DENON a more advance Faroudja DCDi chip is handling the job). I'll get the HDMI cable later but something tells me I won't get any more improvement than what I've got already. But guess what, the "grain-speckle" symptom persists, and this happens on every input used.

Why is this? Is it normal with Plasma sets? inherent with the technology? Will it go away with HDMI? Using the same old Pioneer DVD Player with my 10 year old CRT set (and same quality cables) never showed anything remotely similar. Although this 'noise' is very subtle and only noticeable if you look at it one feet from the screen, I'm worried that this might be a defect. Please help me sort this out so I can be sure this is either a defect or if it's normal.

Second, there is in fact a greenish bias that cannot be corrected with ease using the basic user's menu settings. Without the proper training and living in South America (Venezuela), where can I contact or have an equivalent service like the Imaging Science Foundation nearby? I corrected it thanks to the DENON's excellent built-in picture settings, but this only works while using this deck, so all other inputs are affected.

So, I'm still where I started, no answer on what are those "noise-dancing-speckles" on the close to black areas of the picture (again, only visible at very close range) and no way to calibrate this display to get rid of the greenish bias... unless I find someone capable of poking inside the service menu. *sigh!*

Any help would be quite appreciated.

johnADA · 12-03-2006, 07:50 AM

OK, I'm not and expert, but I'll give it a stab.

Noises like this on any type of TV could be many things and will look at a few.

AC power- Could be something as little as AC interference noises from other sources in the house.
Its suggested at a minimum to use a decent surge protector that also helps eliminate AC noise. I'll add the maximum is a area of high debate and cost. Around a decent $50 unit does the same thing as like a MONSTER one does.

Cables- Another area of high debate that does carry with it some truth. Stock, come with it cables of non HDMI and DVI, suck. On component use 75 ohm, quad shielded cables made from R59 for 3 foot and under runs to R6U for longer. Larger gauge and better shielded on on S-Video ones.

Connection type- Well you found some of that out- Component is better than S-Video, hence DVI and HDMI is better than component.

Sources-
These TV's will only show you once noise issues are corrected and cables are good, ALL the sh*t leftover. DVD players are not equal at all even with the same chipsets. Its up to the software driving them as to how good it may look. Also how you have the DVD player set for output, progressive 480-540P minimum. Then the disc itself. Some companies make DVD discs with very good, clean resolutions and some dont!

Allan Jayne · 12-03-2006, 09:20 AM

Another non-expert opinion.

Does it also happen with ordinary (analog) TV shows?
Do you notice it sitting further away than twice the screen width?

I believe what you are seeing is dithering, which is normal.

That particular brand of screen or display element (not necessarily the whole TV set) may be incapable of showing that many different shades of gray so intervening shades are accomplished by a mixture of a shade too dark and a shade too light, individual pixels varying randomly.

The compression used in ATSC HDTV broadcasts and in DVD's including HDDVD and Blu-Ray may result in effects similar to dithering, called mosquito noise.

Unrelated video hints:
http://members.aol.com/ajaynejr/video.htm

Barton Lynch · 12-03-2006, 05:04 PM

John: First, thanks for the non-expert opinion. I do have a surge protector so I think this is not the issue. I suspect this kind of "noise" as I call it, is some sort of way for the display to produce this level of contrast. All my cables are Monster an MIT, regardless if the debate wether they are overpriced or not, at least they are better that the stock crap included with many hardware.

Alan: Yes, it happens with analog NTSC transmission (there is no HDTV in my country unfortunately) as with any other source or input. If I play with the calibration levels and lighten the black level, this sort of "noise" shifts towards the black area (which by now it is not so black because I lightened it). Not sure what "dithering" is but I sure know what mosquito noise is and it ain't that.

And no, I only notice it when looking at the screen at 10 inches o so, very very close... it disappears even at less that twice the screen height. Thanks Allan.

Anyone else...? how about those experts... no one showed up.

Allan Jayne · 12-03-2006, 10:36 PM

Since you mentioned that, as you raise the black level, the effect shifts down to what should be darker shades of subject matter, or rather the effect affects the same absolute shades of gray, I feel more strongly that you are seeing dithering.

Dithering consists of adjacent pixels of not quite the right color in proportions so that the patch seen at a distance looks like the right color. "Temporal dithering" in video has individual pixels constantly changing between shades of not quite the right color. Dithering is done because the printing process or video display cannot display exactly the right color with all of the pixels the same.

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Barton Lynch · 12-04-2006, 09:56 AM

Allan, sounds quite reasonable, your explanation that is. I've seen this issue replicated on other plasmas since I posted this, plasmas in dealer stores, although not in the same way. Maybe because these displays are not calibrated and have the contrast pushed to the max where shades are limited and therefor this particular level of contrast -where this dithering shows- is not displayed.

This puts some deal of certainty and assurance that my unit is not defective. Although I'd like to find some documentation on this dithering with plasma to expand my knowledge and put this one in my record of NOOB traps. This is my first plasma set, after years of CRTs in my life.

Thanks.

DougR · 12-04-2006, 10:20 AM

Quote:

nd no, I only notice it when looking at the screen at 10 inches o so, very very close... it disappears even at less that twice the screen height. Thanks Allan.

Sit farther back and problem is solved !!

Unless you just like looking for Faults in equipment?

Jeff Gatie · 12-04-2006, 10:47 AM

Quote:

Originally Posted by DougR

Sit farther back and problem is solved !!

Unless you just like looking for Faults in equipment?

I agree. At 10 inches, I'm suprised anyone can even make out an image, never mind critiquing its quality. If it was noticable at proper viewing distances, I'd say there was a problem, but at 10 inches:

Quote:

I am extremely picky with PQ, almost to paranoia levels.

I respectfully say that you are not "almost to paranoia levels", you are far beyond them. Stop obsessing and enjoy your new set.

Paul Padilla · 12-04-2006, 12:05 PM

Barton,

I believe that you're suffering from a bit of electronicus hypocondriac disphoria. (The tendency to obsess that one is seeing or hearing possible flaws in a new, expensive, electronics purchase) It's normal to want to obsess a bit when jumping into your first plasma, though. But really, if you're seeing what you feel are issues and you're any closer than 1/2 the recommended viewing distance, it's time to ease up a bit. Dithering sounds like the most plausible explaination.

You've gone as far as you can with what you have. Get your hands on Avia or DVE ASAP. There's no substitute for standardized tools such as these for calibration. If you're still having problems there are resources out there to help you get into and navigate the service menu, but that can be a little dangerous for a novice.

Sit back (relaxation wise, and distance wise

) and enjoy your new toy for a few weeks and let your eyes adjust. And welcome to the world of plasma.