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Vertical Bands Explained!!

Discussion in 'Projectors' started by Spacecat, Jan 23, 2003.

  1. Spacecat

    Spacecat Member

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    I spoke to a technician at Toshiba today re the faint vertical bands found in many LCD projectors .He said they CANNOT be removed because they are actually the wires in the LCD paneL!!

    He said it was no point in accessing the service menu as the lines are inherent in the structure of the LCD panel it self.
    so basically if they are there thats it!!.

    I find personally that use of an HTPC very much reduces this problem. and a bit of a defocus.


    I am also waiting for a HOYA filter to see if this has any effect.
  2. theritz

    theritz Member

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    Hi Spacecat,

    I don't doubt what you've been told, but I'm not sure its that simple.....

    If this were a physical function of the wires in the LCD panel itself, then they would be as apparent with PC source material as with DVD/whatever. You would also expect them to have a consistent width/position, which I haven't noticed.

    I understand that one of the reasons that vertical banding can be less apparent from PC sourced material (particularly 1:1 pixel mapping) is because vertical banding can be minimised or eliminated using the clock phase adjustment. In PC mode, Auto Adjust can be very effective, but additional tweaking of Frequency and Phase have the added benefit of micro adjusting for any residual noise, dot-crawl or banding. I am not expert in this area, but I imagine that the vertical banding issue arises mainly as a function of out of phase cancellations arising in the bias drive of the LCD panels - this could be related to internal scaling being done by the projector, which would explain why 1:1 pixel mapping is cleaner, but not completely clean, as fluctuations in the bias drive to the panels could cause residual banding to be present.

    I really hope someone else chimes in here - if I've got it wrong I'd love a definitive lecture - Gordon, where are you ???


    See ya,

    Sean G.

    Edit: Spelling (!) and: I just noticed your comment on Hoya - I've recently gat one of these and now wouldn't be without it - great for better blacks and v. improved colour balance, but it doesn't do anything about the vertical banding issue for me. SG.
  3. John_N

    John_N Guest

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    ;) I noticed the word 'lecture' carefully used there... Still haven't forgotten eh? :)
  4. ROne

    ROne Member

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    No, I am not having this.

    Vertical bands and screen door are often interelated as the same artifact. Screendoor is a physical element of the panel, the gaps between the pixels. Vertical banding is a 10 pixel (or so width) where the pixels are darker or lighter than the surrounding pixels.

    Hence on some scene's such as fog or clouds you can get what appears to be a wire running the height of the screen, if you stick your nose up to the screen you will the see the pixels that make up this line form a darker (or lighter) line, which is space in equal widths across the screen.

    Very often confused with screendoor, I can assure you that it is possible to get rid of the vertical bands as I have done this on the service menu of my z1, what I am actually doing though is difficult to say. You obviously can't get rid of physical structure with service menu tweaking.

    On that note it is worth mentioning the Z1 has very, very minimal screendoor out of the box (as good as my 1280x720 projector) but really poor banding.
  5. theritz

    theritz Member

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    John_N,

    ;) I assume we're on good terms......

    Rone,

    It didn't occur to me that you would have thought of it as a mix up with screendoor..... Vertical banding is, as you point, out a whole different kettle of fish .:eek:

    Any chance that you're adjusting the panel bias through the service menu of your Sanyo ?? Service menu access isn't available for the AE100 - it requires a hard link and service software to do service level adjustments :( .

    Sean G.
  6. olaiho

    olaiho Guest

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    Spacecat,
    sounds like Toshiba is trying to avoid having to repair your projector for vertical banding, trying to get you into accepting what is clearly a fault in the projector.

    Regards,
    Olaiho
  7. ROne

    ROne Member

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    Ritz,

    I don't mix it up with screen door but many, many people do.

    Somewhere along the way your knowledge has to be learned and with subjective things such as picture quality it's sometimes difficult to relate concepts such as screendoor/vb to an audience.

    As vertical banding/screen door can both be described as vertical lines running down the screen then perhaps its very easy for people to confuse the two.

    Having owned several projectors now and hear people talk of severve screen-door on the Z1 one can only assume they are talking about the VB. Cause there's bugger all screen door on the z1 at most reasonable ( 1.5 upwards) distances.

    Haven't got a clue what is being changed on the service menu (I am waiting for the manual.) but it works.
  8. Spacecat

    Spacecat Member

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    well i have had my Toshiba MT1 for nearly 2 years and to be honest i am very pleased with it. The vertical bands are non existant 90+% of the time and it is very solid re its picture quality.
    In many films its not noticeable at all!!.However like everyone here i want perfection so if i could stop it completely (i.e in the foggy or misty scenes in which it appears) then i would be most happy.I did take it to a toshiba service centre (before i got my HTPC) and was using a dvd player and they did the service menu check and said it was perfectly set up and we couldnt see the vertical bands!!

    The HTPC had a massive effect in reducing this!

    The screen door on the MT1 is a non issue in my eyes and the contrast is also good.It is also very reliable and well built and has never caused any problems which is an underestimated virtue in a projector, NO DEAD or DODGY pixels

    Has anyone with a SONY HS10 seen these vertical bands on their projectors
  9. theritz

    theritz Member

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    Rone,

    I wasn't for a moment suggesting that you had mixed up screendoor with vertical banding !! The fact that your post made such a clear distinction between the two is ample evidence of this.


    I'm glad you found a fix in the Service Menu - have to say I'd love a tweak at the AE100, but it just ain't do-able !


    Sean G.
  10. John_N

    John_N Guest

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    I haven't seen these bands on my HS10 yet... I don't really want to see them because it's probably a bit like the horizontal wire on a Trinitron screen. Once you see it - it annoys you.

    theritz: Yeah of course :) . Sorry if the tone of my posting was a little terse - hasn't been the best few days at work recently. ;)
  11. Comer

    Comer Member

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    I have the Tosh MT3 and using Svideo the vertical banding hit me within the first hour of viewing the projector. It is not something that I believe anybody could ignore particurarly if viewing the pj for a few months. I sent it back to Toshiba who said they could adjust the settings to reduce this banding. If these bands were being caused by "wires" in the panels I don't believe that it would be possible to "adjust them out of the image" Upon recieving the projector the engineer told me (over the phone) that they all thought that the vertical banding was very minimal on my pj especially when compaired to a test projector they had. In fact he said that he would have preferred mine to the pj they had. As we all know vertical banding varies from pj to pj. I was previously using a Hitachi data projector with an apalling picture quality but vertical banding was not near as evident as on the Tosh MT3. I actually believe that it is a result of a poor scaler in the pj (can't back this up, it's just a hunch).
    Spacecat, I agree that vertical banding is almost invisible using a HCPC but there is no improvement using a progressive signal to the component input of the pj. Also (to backup my [shaky]theory on the scaler causing the banding) they are alot more evident when sending the pj a 640X480 signal than 800X600. In fact there isn't a huge difference between 1027X768 and 800X600, something to do with scaling up being better than scaling down???
    If I watch at 800X600 @60hrz I get an excellent picture but with constant tearing. If I reduce the resolution to 640X480 the tearing disappears but the vertical banding returns (not nearly as bad as svideo or component in) and a slighly fuzzier image. So now I watch at 1027X480 and the vertical banding is seldom noticed, the tearing is less than at 800X600 and the reduction in picture quality over 800X600 is really not noticable (don't ask me why. Am I happy? What a stupid question!!! :D, I'm into home cinema, I recon that I'll never be happy again. That's the nature of this beast (hobby)

    My conclusion (sorry for rambling on there) is that the MT3 (and possibly MT1) while are very realiable with wonderful picture quality from a HCPC also have a few serious problems (vertical banding, tearing and poor scaler). That said absolutely no one else who has seem my projector has ever complained about these problems to me, even when I point them out

    Edit: the quality of the dvd transfere also has an affect on the vertival banding

    Conor
  12. Gordon @ Convergent AV

    Gordon @ Convergent AV Well-Known Member Assured Advertiser

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    The man to speak to about this is probably Richard Ansell. It is NOTHING to do with the wires for the panel.....what is that guy on?

    TheRitz is on track. Banding can be helped by these adjustments but you may also find similar banding on a CRT when used with an external video processor......or on a plasma display even. I believe it has to do with the bandwidth limitations of the adc/dac's amongst other things. ie There aren't enough bits to accurately describe the full greyscale. Off board video processors and HTPC's generallyare much better in this regard.

    The GEFORCE graphics cards exhibited this issue and it was one of the reasons that many moved to the Radeons for their Hi-end HTPC's. Well, that's my thoughts but I think if we get Richard to pitch in we'll get some better more accurate info (cos I don't know everything...)

    Gordon
  13. Chris Frost

    Chris Frost Active Member

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    :eek: shurly shome mishtake ;)

    Regardsh,
  14. Mr.D

    Mr.D Active Member

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    I could never understand what people were talking about when they mentioned the ae100 and vertical banding. Then I twigged as I only ever use it in conjunction with an HTPC and as I'd adjusted the pixel clock and phase using mark rehjon's handy test pattern ... no vertical banding.
  15. Kramer

    Kramer Guest

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    All this talk of scalers, source, clock/phase adjustments etc...

    My AE100 exhibited VERY noticeable vertical banding with NO source connected.

    Just displaying the R, G & B screens in the service menu showed banding on all three colours - especially the red & green.

    Tell me that it's source related - rubbish IMO.

    BTW, NO, I repeat, NO vertical banding on the HS10.

    There are two types AFAIK, banding caused by source/adjustment, & more worryingly, inherrant banding of the panels which, on ocassion can be improved/cured by tweaks of the panel drive in service menu.

    My 2p.
  16. MrGrumpie

    MrGrumpie Active Member

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    I've never noticed vertical banding on my Z1, except with the X-Box. Very noticeable on that (interlaced, via component).
  17. theritz

    theritz Member

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    Gordon,

    "TheRitz is on track" - Phew !! thank heavens for that !

    "I think if we get Richard to pitch in we'll get some better more accurate info (cos I don't know everything...)"

    WHAT ??? Don't believe that !! Still, if we could get Richard Ansell to give us the low down......




    Kramer,

    What the **** are you doing up at this hour ???? :D :D :D

    Quote 1:


    My AE100 exhibited VERY noticeable vertical banding with NO source connected

    Comment:
    Don't see it on mine without a signal, maybe you would - and I'm glad I didn't get you to check !!!! :p - when you were around I had a dodgy Svideo connection for the DVD, and the picture was fairly wrecked with banding - new connection, banding still there but far less ( AE100 is scaling XGA from ProV, I haven't tweaked the clock phase on this but will have a go later.) Banding from laptop = minimal, imo, and have tweaked clock phase for improvement.


    Quote 2:

    Tell me that it's source related - rubbish IMO.

    Comment:
    Not source as in dodgey dvd transfers, agreed, but cabling/dvd/pc all have their role to play, and can provide lots of anomolies for some (not always efficient or effective) scalers in pjs to deal with.


    Still searching for the definitive techno-answer........




    Sean G.
  18. Spacecat

    Spacecat Member

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    i have to agree with comer on the banding issue as i have noticed that some dvds it practically has none and on others it has quite a bit.
    i.e spiderman had a lot but crouching tiger had NONE AT ALL!!

    i asked the Toshiba bloke how to get into the service menu and he said it was a special programme run by the r232 connection.

    however he said that THEY COULD NOT LET ME HAVE THE SOFTWARE!! as people were bodging up their projectors !!by messing up the settings.

    Im gonna phone again tomorrow and ask to speak to someone in charge!!my projector is out of warranty i think i should be allowed to play with it!!
  19. ROne

    ROne Member

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    Some DVD's seem to exhibit greater intensity in their transfers that coupled with running of HTPC (which passess a cleaner signal) can mean more perceived contrast to the panel, hence why some DVD's seem liket there is more or less banding.

    Watch something like Black Hawk Down where there are lots of high-intensity shots shooting against compressed black detail and you will see hardly any banding.

    However then watch a very flat transfer of a subdued film and the banding issue can be really annoying.

    See my info for improving banding on the Z1

    http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=211744
  20. Mr.D

    Mr.D Active Member

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    Didn't notice any banding on spiderman region1 on my ae100 through htpc.
  21. Spacecat

    Spacecat Member

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    bought a hoya filter today so will do some tweaking tonite!!

    my spiderman dvd was a region 2, the main bit where vertical lines are apparent is the scene where spiderman is coming round after the green goblin has gassed him.The scene is on the roof and theres lots of steam/smoke which is bad for highlighting this problem
  22. Paul D

    Paul D Active Member

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    This banding was a problem i had with my Toshiba MT1 LCD.
    At first i thought it was source related, as certain DVDs were affected more than others.
    Then i found solid light shades ie clouds/smoke displayed the banding whatever the DVD.
    I then found using a HTPC versus svideo, also "seemed" to reduce this affect.
    Setting the dot phase also seemed to reduce the banding.

    BUT...

    Nothing i did completely removed it.
    In fact i noticed that the banding (8-10 pixels apart) was there with no source present. Ie it was panel related and not source, so all the source tweaking was doing was to lessen the impact etc.

    I then switched to the Sony VW10HT, and hooray! banding gone.

    BUT WAS IT?

    Although it was invisable from normal viewing distance, which is very close with the high resolution panel, the banding was still there!.
    The only difference being that since the pixels are smaller with the same screen size between the MT1 and W10HT, the banding was about four inches apart on the MT1 and less than two inches apart on the W10HT.

    So it left me assuming that it is a LCD thing, but higher resolution panels solves the problem by shrinking it etc.

    I really did love that VW10HT, it was only the poor contrast/black level tha let it down. The picture was stunning otherwise... ;)

    eee when i was a lad eh!
  23. G a f f e r

    G a f f e r Moderator

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    Don't know about vertical banding but my system seems to give me some kind of horizontal banding :)

    'what the hell is this?' thread
  24. DRulz

    DRulz Guest

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    Does the Panasonic 500u exhibit vertical banding?

    Jason
  25. pierrev

    pierrev Member

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    I can confirm that I see vertical lines on my ae500 particularly in smoky scenes or large expanses of pale colours - I saw them described on a review I read, as rather like the streaks on the titles of 'The Matrix' only they are still as opposed to moving.

    Having gone through many threads on this subject - what I would like to know is if any AE500 users have tried to use a (Hoya ?) filter and NOT had any success - the lines I see are clearly inherent in the machine (as well as in the other one they had at the shop I bought it at) and so I would be surprised if changing the connection (to DVI) would help (though I am intending to take my PJ to a try out on a friends Mac that does have a DVI output ... just in case it helps)

    one tip I can give (at least to those whose eyesight matches my own) is to take your glasses off when watching the PJ - lines virtually disappear - I normally wear glasses for driving and watching telly but not at other times - I guess this is similar to putting the pj slightly out of focus to diguise the lines !!!
  26. memorgan

    memorgan Member

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    Having the same problem with my Epson EMP S1, had 4 units from Epson, all with banding! Tried 3 different DVD players, changed all interconnects, from composite to Svhs, and still Epson tell me it must be " Environmental", even tho its been set up in 3 different locations. Just becuse they cant duplicate the banding and green colour shift to the left side of the screen in their labs. I mean a lab is as good as it gets right? They havent looked at this " in the wild". What is there left for me to do to eliminate this problem? Someone mentioned hidden menus or something, I know mine has one, how can I access it, and what should I do once in there?

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