Welcome, Guest. Please login or register.

Author Topic: Dirty Screen Effect on LCD, LED and Plasmas  (Read 22657 times)

0 Members and 1 Guest are viewing this topic.

snadge

  • Guest
Dirty Screen Effect on LCD, LED and Plasmas
« on: 25 November 2011, 20:48:07 »
Advertisement
Anybody wanting to know what those funny marks are they see on their TV screen should read this post i made on another forum as it describes what it is...

im making it a sticky for others to refer too


For over 2 years now ive been trying to find out exactly what this 'Dirty Screen Effect' is that seems to affect almost all LCD displays.... ive had 3 LCD's and all of them had it too some extent... A lot of people don't realise they have it....like my dad... Ive noticed loads of LCDs with it in stores aswell and expensive brands are not immune from it either...

Ive thought about it and searched the web but found no information that supports a possible explanation of what it is and how its caused...


I have come to my own conclusion and would like others to Input on this to see if we can pinpoint what this horrible on-screen artefact is that we have to put up with - of course I could be totally wrong, this is just me thinking out aloud....

...Cell Warping...
it seems to happen because a 'group' or 'band' of pixels (cells) have become slightly 'warped' either with heat or just shear flexibility from the weight and orientation of the thin screen that the light passing through these 'cells' is no longer in direct line of sight and 'appears' as slightly darker patches on the screen to the viewer, I think it is more likely to be from flexibility and weight of the LCD panel itself and can be worsened with prolonged viewing (heat from back-lighting making it worse) as was the case with my first LCD, if you held up a 42" LCD Panel itself in your hands it would warp and twist and the light in the bends/twists would darken (just like your PC/Laptop screen does when you press your finger on it) ...
- this would explain also why we only see it with light/pastille colours and mostly noticeable when the object/camera pans around as the colours in the image are bright and uniform, but when they pass through the 'affected area' on screen they stay slightly darker than the rest of it.

This obviously can not be 'repaired' and seems to be a flaw with most LCD screens, the only way it can be overcome is if the manufacturers come up with some new type of panel that is stronger/firmer with perfectly alligned cells.

My first LCD was more in a uniform banding pattern of blotching rather than random blotches like my last and current LCD, the first one didn't have any noticeable banding at first but after prolonged use (9 months) it started to appear and got worse, the uniformity of it suggested it was the LCD screen becoming weak from heat of the backlight and causing it too warp...

again I must stress this is just me thinking out aloud but I do think its a good explanation of what could be happening and Iam calling it Cell Warping until a better explanation comes along

anyone else care to add to this...feel free

Offline CappySpectrum

  • Super-Hero Member
  • ******
  • Posts: 1453
  • Gender: Male
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #1 on: 28 January 2013, 19:53:04 »
I've noticed this effect on one of my HDTV's (720p max) but it was an adverse effect from a Creative subwoofer right below the TV on a unit. Within 2 centimetres. Sadly I didn't know it was going to create this effect or distort anything. This happened 2 - 4 years back.

Most of it slowly faded away. It used to be like a blackish diagonally wavy weave low right to close top left across the screen. Other parts it left like vertical finger trails dragging down the screen just slightly off centre. It's only noticeable on low/dark colours, like cement/stone and sometimes shows a green tint to it. Sometimes it shows on certain low greens dependant on the football ground lighting.

The subwoofer took a long time for the problem to show on the screen.
Originally known as Quasimoto

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #2 on: 28 January 2013, 20:00:22 »
how is it do you think the speaker caused the problem..?

some people have reported it appearing after a while, getting worse...and getting better..

on my old and first BUSH LCD screen it wasnt there and slowly appeared over time, our replacement LG had it soo bad I took it back and got a different LG model...this one had it too but barely noticable and has remained about the same for the 5 years weve had it.

its more noticable on pastille colours when camera pans around.. such as white washed walls etc,, cos the slight variation in shade as the camera pan's makes it noticable

Offline CappySpectrum

  • Super-Hero Member
  • ******
  • Posts: 1453
  • Gender: Male
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #3 on: 28 January 2013, 20:03:58 »
how is it do you think the speaker caused the problem..?

Because it sat for years before the subwoofer was placed there and no picture defects. Then when I discovered it, I started checking up on the speakers. The subwoofer isn't magnetically shielded (it says to keep a 2ft distance from appliances) but the satellites are shielded. It's also quite a big subwoofer and must have quite a big magnet. So picture distortion...
Originally known as Quasimoto

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #4 on: 28 January 2013, 20:17:21 »
the picture distortion from magnets you mention is usuallyt affecting the signal directly and not any physical part of the screen, and mostly on CRT type TV's due to the parts they use and the way they display, IMO I dont think your speaker caused any of your problems (I could be wrong), the finger trail lines down the screen are classic symptoms... my first Bush LCD had this in spades and it slowly got worse over time. my new one has 'patches' of it

what is the size of your screen?

personally I think its exactly what I describe in my post, the heat from the backlights and components softens the LCD screen and causes it too bend by very tiny amounts under its own weight...after all it is upright and not lying flat on a flat surface, the pixels that appear as darker patches are slightly out of line of sight compared too the rest of the pixels and hence appear 'darker' - grab your laptop screen on the right had-side and press your thumb on and off the screen and you will see parts of the screen darken slightly above and below your thumb....same principles..

I think all LCD /Plasma screens will suffer with this too some degree until they invent some type of stronger screen that wont flex

Offline CappySpectrum

  • Super-Hero Member
  • ******
  • Posts: 1453
  • Gender: Male
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #5 on: 29 January 2013, 00:36:29 »
what is the size of your screen?

37" Samsung LE37S73BD.
Originally known as Quasimoto

Offline runITdirect

  • Getting There
  • *
  • Posts: 36
    • run-IT-direct.co.uk Supplying Telecom & Network Products Online
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #6 on: 31 May 2013, 11:50:56 »
Only skeeted through this but a what type of backlight do your TV's have? Can you post a picture of the problem? A speaker shouldn't affect an LCD screen, not like the old CRT's anyway but I have a theory in my head if your TV employs the old type of back lighting rather than LED.......

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #7 on: 31 May 2013, 13:30:18 »
what is that theory? would like to hear it :)

mine were all CCFL TV's

Offline runITdirect

  • Getting There
  • *
  • Posts: 36
    • run-IT-direct.co.uk Supplying Telecom & Network Products Online
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #8 on: 31 May 2013, 13:34:47 »
The CCFL tubes discolour over time, much like the versions you get lighting garages etc.

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #9 on: 31 May 2013, 14:00:15 »
Yeah that's not what's happening here...  Its not discolouring, but patches or  streaks slightly darken but only really noticeable when camera pans because the slight variations in shade on the screen make it stand out..  A classic example was with those Diy programs and they would pan the new room that was whitewashed and you'd see it loads, my sister's led TV has it a bit too... I still stand by my theory of light from pixels shooting off slightly out of alignment compared to neighbouring pixels.. Probably from the sheer weight and flexibility of the screen itself..  Press on your laptop screen and you will see it darken where you press it as light is not travelling in parallel with light from other pixels...  They need to design a more robust panels with a better manufacturing process...  Least that's what I think it is..  I out this on av_forums years ago and drew some interest..

Sent from my Sony Xperia Miro on Tapatalk


Offline runITdirect

  • Getting There
  • *
  • Posts: 36
    • run-IT-direct.co.uk Supplying Telecom & Network Products Online
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #10 on: 31 May 2013, 14:09:47 »
Are they like this from new?? Can't say I've ver noticed it on my laptop screen but that is only 17".

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #11 on: 31 May 2013, 14:24:57 »
Smaller screen less affected,  only seems to large screen tv, laptops don't seem to suffer from it, too small, I think large screens sheer weight n flexibility, also a lot of people can't see it,  only a trained eye..  My dad's had it,  he couldn't see..  My sister's led had it..  She couldn't see,  until I pointed it out (which she now hates me for lol)

Sent from my Sony Xperia Miro on Tapatalk


Offline runITdirect

  • Getting There
  • *
  • Posts: 36
    • run-IT-direct.co.uk Supplying Telecom & Network Products Online
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #12 on: 31 May 2013, 14:49:30 »
But is it there from new? That is the important bit, if it is then i would say it is more likely due to digital pictrure processing??

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #13 on: 31 May 2013, 15:30:57 »
some can be there from new.. some get worse over time...some arent there from new and appear after X amount of time

this (what I'm on about) is definitely not digital picture processing... defo 100% not.  if you seen it as much as i have you would know, on my bush TV it wasnt there to begin with but appeared after few months and got worse, I think that was caused by heat from behind the screen causing the LCD panel to flex in the tiniest amounts causing the light from the cells to mis-align with the others (looking like darker patches on the screen) we got rid of that bought an LG that had it so bad I got it swapped after a few days at Richer Sounds for different model and this one had it too but nowhere near as bad... had this one 5 years now.. I just accept that most TV's have it (LCD/LED/Plasma) but getting one that doesnt have any or has it a little is what your hoping for when your new one arrives boxed lol...

its not something one can take a picture and show either because its something that only stands out when theres motion on the screen, you have to be there in person with someone who can help point it out... its not total uniformity of brightness across all the cells..due to the reasons already explained, well thats what I think causes it and it makes sense when you think about it, LCD screens support their own weight for the most part, so it would make sense that sections of the screen might twist and warp (ever so slightly) causing pixel cells fire light off in slighty different direction, those patches appear 'darker' - like i say a simple analogy is press your thumb on your laptop screen and watch it darken and lighten...then settle one you stop... also laptop screens dont have as much heat as larger TV screens... i think that contributes a lot too it (making it worse)

Offline runITdirect

  • Getting There
  • *
  • Posts: 36
    • run-IT-direct.co.uk Supplying Telecom & Network Products Online
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #14 on: 31 May 2013, 15:41:57 »
I think what you may be describing is the latency of LCD, if the pixels are showing one thing then the scene changes rapidly there will always be latency, that is a restriction of the modern flat panel. Not sure if OLED will be the same?? I can't see it being heat if Plasma screens suffer from it too TBH.

Offline Inactive

  • Super-Hero Member
  • ******
  • Posts: 1709
  • Gender: Male
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #15 on: 31 May 2013, 15:44:11 »
I have witnessed this on my LCD in my bedroom, but I have never seen it on my Plasma in the living room. :-\

Offline CappySpectrum

  • Super-Hero Member
  • ******
  • Posts: 1453
  • Gender: Male
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #16 on: 31 May 2013, 15:56:47 »
Are they like this from new??

No, mine took several years for it to show but it only happened when I has the subwoofer below the left hand side of the TV over a long period of time. However, thats not the case now. After several years with the subwoofer gone, tv in another room, the marks has nearly all faded away. It's been a gradual process fading in to heavy black marks to fading away back to a normal picture.

Mine is CCFL as well.


An old photo before it got really bad. 31 October 2008

The below wave has gone. It's like finger trails vertically of the same look off centre.



[attachment deleted by admin]
Originally known as Quasimoto

snadge

  • Guest
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #17 on: 31 May 2013, 16:56:13 »
Heat not always the cause,  it can make it worse,  it not latency because the pixels remain dark in one area,  it's not something that follows across the screen, it's fixed but panning shots reveal the patches due to the variations in light as the camera pans across...  I've never seen a plasma,  just assumed they have it to because the basic design is still the same,  manufacturing processes might be better now and new tv's may have it less..  I'm not even sure cappy spectrum is getting the same thing, can't see that picture very well on phone,, also the symptoms I've seen are not caused by speaker magnets...  His could be some thing else

Sent from my Sony Xperia Miro on Tapatalk


Offline runITdirect

  • Getting There
  • *
  • Posts: 36
    • run-IT-direct.co.uk Supplying Telecom & Network Products Online
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #18 on: 31 May 2013, 17:04:33 »
the pixels remain dark in one area,  it's not something that follows across the screen
Sounds like pixel retention to me. LCD & Plasma are completely different, about the only similarity is they are both flat & thin!

Offline CappySpectrum

  • Super-Hero Member
  • ******
  • Posts: 1453
  • Gender: Male
Re: Dirty Screen Effect on LCD, LED and Plasmas
« Reply #19 on: 31 May 2013, 17:56:27 »
I'm not even sure cappy spectrum is getting the same thing, can't see that picture very well on phone,, also the symptoms I've seen are not caused by speaker magnets...  His could be some thing else

I thought it was. This is what it looks like today, it's nothing compared to what it was. It was so bad if any faces were on the right hand side of the screen, the skins tones were coming out blood pressure/slapped purple. Plus huge diagonal black weaves across the screen.



[attachment deleted by admin]
Originally known as Quasimoto

 

Powered by EzPortal