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547 Views 10 Replies 6 Participants Last post by  cmjohnson
looking at plasma in particular, fixed pixel devices in general, I see a lot of what used to be called "solarization".

Blotchy skin tones everywhere. Like the bedroom scene in the beginning of "HOLLOW MAN"

chapter 11 of FINDING NEMO has good examples. The angler fish "lamp" has concentric rings of light instead of a continuous fade. This not a back level problem.

Seconds later the effect is seen on the safety green strap of the goggles. As the angler moves around the light intensity changes and the strap show clear steps in shading. Close up of the strap looks really blotchy.

The Korean LCDs look the worst. The Fujitsu and Loewe plasmas look bad.

A paired Faroudja DVD and DLP projector shows none of the effect nor does a Madrigal MP-9 driven by a Runco scalar and Lexicon DVD. I use a HTPC and a Marquee 8000 at home and have never seen it there.

Having moved several DVD players around, the DVD player is not the culprit. We also tried S-video and 480i and 480p component.

Admittedly the Runco 4404? scalar is about $20,000 and the merits of the HTPC are well known.

Is the eye so sensitive to suble color shades that most processing technology is visible?
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Welcome to the imperfect world of digital!

Well, 'welcome to the world of digital' is a bit harsh.

Would any of us trade the image from DVD or from a HDTV broadcast for an analogue VHS, or LD image?

Probably not.

It is not an inherently 'digital' problem, you can digitise stuff to way beyond the point of visibility re banding etc.

On plasma screens the banding is because the pixels can be either full on or off with regards to brightness. (unlike lcd and crt where they can vary the 'brightness' of the pixels).

They then do a tricky 'shuttering' type system to get the variance in brightness. Various manufacturers do it with varying success.

Some Plasmas are just awful, and it is instantly noticable some like the Fujitsu 1024x1024 models do it very well, and you don't get blotchy skintones etc at all. But it is getting better with each evolution of the sets.

(But remember to look at them from the correct viewing distance before getting too picky)

The problem is one of a good implementation, coupled with the not as good contrast ratios. But on good sets it is not noticable, and bad ones it is.

You know if you judged all crts on the performance of a sony 1000 or a barcovision 600, (without ever seeing a D90) you would think that crts were pretty crappy with their horribly visible scanlines etc etc.
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Be careful in your comparisons.

I have a substantial laserdisc collection, which I still use.

SOME of those laserdiscs have a picture that's better than MOST of my DVDs.

Stop defending digital dithering dokworm.

They suck, and one of the main reasons why they suck, is most of the LCD's, DLP's Plasmas and LDC TV's I've seen dither, really badly, like a PC monitor at 256 colours. I'll admit that some of the new ones may not, but I don't care.

I'm sure all the paranoid digital guys who trespass here will jump all over this....but I don't care about that either, it's amusing.

Oh, yeah...

NONE of my LD's have ever shown any digital artifacts. I'm particularly likely to notice that effect that occurs on DVD when a complex scene is panned SLOWLY or the camera pulls back. Whatever you call that particular form of dot craw/compression artifact, be it dithering or whatever, LD's and other analog sources don't have it.

That does not necessarily make laserdisc a superior format, but it DOES have its strengths.

ya'know what? I was hoping someone would confirm my suspicion that the input A/D stage is where the problem lies. After all, the Runco scalar does not show the problem. Nor does the Faroudja DLP that has no A/D step in the signal path.

is this because the Runco has a very good A/D and the Faroudja has none?

if so, then this is not a dithering problem but a lack of bit depth.

can any body confirm that DVI input looks OK?
There are 2 places where this "Effect" can be injected into the signal.

1 Any conversion from A to D or D to A


2 Any conversion from D to D where one side of the conversion is at a lower bit-count than the other.

so, for-instance, if you have an all digital signal, and we look at one channel, say get Green or Lum, that has a resolution of 8-Bits per sample on the source (a DVD), but the display device, (a DLP or LCD) can only resolve 6 bits, then there is going to be some banding.... and in-fact, if the source DVD had really smooth tones, then we will see it more than if the DVD had a grannie film like quality.

now, if we go up to a higher end DVD player, but keep the same crappie LCD with DVI, now the DVD (8-Bits) gets up-sampled to 10 or 12 bits and then back down to an effective 6 at the low end display device! Yikes

on a Digital to analog to digital path, as in a DLP or LCD without Digital in. we have the same 8 to 12 bits per sample, then we have to hope that the D to A in the DVD Player is good, and can resolve all that info (probably it can only resolve 8 bits, even if our player up-converts to 12), then we take that to a input device that has a A to D that can probably only resolve 7 bits.... then too a display (LCD or DLP Panel) that can probably only resolve 6 bits.... now we are really seeing some crunching!

we rarely see this effect on CRT Projectors because we have an analog signal path, so unless we are using a DVD player with a really pour decoder, what comes out should give us the full 8 to 12 bits of Analog bandwidth.

and none of this really even starts to mention the mess that happens with compression/decompression algorithms... That's another big can of worms!

Just my 2 cents....

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Quote: Mark_A_W:

"I've seen dither, really badly, like a PC monitor at 256 colours. I'll admit that some of the new ones may not, but I don't care."

Now that is just silly. New ones may not but you don't care?!?!

That would be like in the early days of crt saying, 'The ones I have seen all have horribly visible scanlines - the new projectors may not but I don't care"

The best of the plasma screens don't suffer from colour banding at all, and the second tier products suffer from it a little, but not at viewing distances - the erst look horrible - granted.

Digital is not inherently bad - Take a look at a high quality HDTV broadcast and tell me you like analogue TV or laserdisc better.

Get over the digital = bad, analogue = good thing people!!

BTW Very few of my laserdiscs look better than my dvds (and I have over 300 LD's), a lot of my LD's suffer from 'sparkles' and the horrible chroma fringing. But when I compare my best LD transfers with my best DVD transfers, the DVD wins hands down.

Anyone can pick a crappily transferred disc to compare to a good transferred one. Laserdisc does have its strengths, but I almost never use mine anymore.

(Happy PG9+ Owner)
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This may have been taken care of, but if the set is not calibrated correctly for proper grey scales etc... you will get the "solarization" inherent in the compression algorythms in MPEG. An example would be that your gamma or brightness is set too high.

In the compression algorythms of MPEG redundant areas are blocked together to minimize the amount of digital info to encode them. When these redundant areas are over a larger gradation (eg; skin tones) then the blockes can be large and threshold jumps between blocked layers will look crude.

I am getting bogged down so I will shut up now.
So far, the best single scene I've seen yet on any DVD that will tell you if your projector's contrast, brightness, drive, and G2 settings (and gamma, if you have it) are set up right are the scenes in the whale's mouth in Finding Nemo. The foam on the waves in there will show up solarized if your setup isn't really good, or at least that's been my experience.

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