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light streaks in dark scenes

Discussion in 'Projectors, Screens & Video Processors' started by NickBull, Jan 23, 2002.

  1. NickBull

    NickBull
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    This is a problem I've started to notice more. In dark scenes like in the Mummy Returns, where there is a bright light source liek the flaming torcches, I get a light horizontal band across the screen. A bit like a ghosting effect.

    Is this to do with an anamorphic squeeze due to using the 16:9 scree, the age of the pj, or something else?

    Is it possible to tweak it out at all, or to make it less noticable. It's only noticable on certain scenes, but any improvement would be good.

    Thanks

    Nick
     
  2. Alan Westy

    Alan Westy
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  3. NickBull

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    Alan,

    Just read the first line and it sounds like just the thread I'm looking for. Thanks a lot for the link.

    Nick
     
  4. Roland @ B4

    Roland @ B4
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    I'm aware of this issue and working on a fix but the engineer who has it in hand is a bit slow. The 708 has a mod which should be done.

    I'm afraid its just something that CRT's in general, do. but only at very specific low grey levels.

    I'm also meeting with Barco on Friday raise a whole load of technical issues i'll put it on the list.
     
  5. NickBull

    NickBull
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    Thanks Roland, I didn't notice it much at first, but The Mummy Returns highlighted it as it has a lot of flaming torchlit scenes.

    I was worrying it had got worse but not I just realise that everyone has the same problems.

    To be honest I'm more concened about some problems with the DVD software I'm using, but have just had the Theatretek stuff delivered and hopefully that will be the end of them.

    I think other people ojn the forum are right when they say that you never stop trying to improve things!!

    Cheers

    Nick
     
  6. Roland @ B4

    Roland @ B4
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    I had to buy a copy of a DVD to prove to Barco NV that it was happening.

    Specre will know the scene he made me watch it.

    Don't expect a quick fix for this but it will come.
     
  7. NickBull

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    It's only the very od scene, even Hannibal wasn't that bad to watch and that has a lot of dark scenes.

    I suppose small adjustments to brighness and contrast could make a difference, but to be honest It wouldn't be worth compromising hte rest of th picture for these few scenes.

    Still be interested to know if a solution is found (you could do a package deal with that and the fan mod!)

    I'm still stuned by the quality of the picture I'm getting, esp on an old pj.

    Nick
     
  8. tryingtimes

    tryingtimes
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    Yes, Roland I hadn't realised it was only on dark grey scenes and not black.
    My experiments last night (I was trying to get a photo for AVS) revealed that on a black desktop it wasn't there. During most dvd's though where the black level is set just slightly lighter than black it was present all the time.
    Very interesting.
    What does the solution involve Roland?
     
  9. Roland @ B4

    Roland @ B4
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    It will almost certainly need a hardware adaption.

    I'm on my way to Barco right now and will press the point but as I said I don't promise a quick fix.
     
  10. chrisgeary

    chrisgeary
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    was there ever a resolution for this?
     
  11. Barcoing Mad

    Barcoing Mad
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    Barco NV weren't aware of the problem? Incredible.
     
  12. Nick Cartwright

    Nick Cartwright
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    I was NickBull (reference to Bradford Bulls RL team, not my last name).

    I didn't get a resolution, but then the problem isn't that bad. I did a lot more setting up of the contrast and Black Levels using the simple test screens on the THX optimiser. If you get the black level right on that then it reduces the problem to the bare minimum. Mostly due to DVD's not encoded with very good blacks in my opinion!

    I was suprosed to see this thread near the top after being away for a while. I can honestly say that it's only in very few films that this is actually noticable.

    Nick
     
  13. Roland @ B4

    Roland @ B4
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    Hey this takes me back.
    Whilst there was never a proper hadware fix and it only affected the MEC tube version of the 808. I notice barco have gone back to the MEC tube ij the Cine 8 and the issue has gone from that.
     
  14. Nick Cartwright

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    Takes me back too. To be honest, after setting black levels correctly I hardly notice this anymore.

    I think the trick was that I lowered the brightness on the PJ and use the controls on Theatretek to calibrate using the THX optimiser.
     
  15. Paul D

    Paul D
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    I believe Mike Parker over at AVS now has a fix/mod for this.
    Do a search in the CRT forum for more info.

    Roland, maybe you could contact MP for the Mod and offer it over here etc.
     
  16. crteaman

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    OK I think I can explain this guy's, the problem you are seeing is called luminescence peaking, this is not a problem on the Panasonic tubes but is in fact due to the RGB amps fitted to the data models.

    If you notice, the BG 808s does not have this problem, but its not because of the sony tubes its the RGB amp.

    The high Bandwidth amp (the integeral one with the big heat sink) is the fix, Barco went over to the Panasonic tube because its beam spot size is 15% (they used the % not I) smaller, in fact many of the simulator units and those supplied to the likes of SEOS had Panny tubes as standard.(with the High spec amp)

    So in a perfect world, you need the Panasonic tube (fitted to 808s data) but with the High bandwidth RGB amp (fitted to the Graphics with sony tubes), Henry and I performed this very task for two customers on this forum,one of which is 'GODFATHER' who would no doubt like to tell of the results in his own words.(i think he's in france at the mo)

    The other thing with the panny tube is because of its physical shape, you can use more tube face than the Sony tube.

    Tis true barco were not aware of all of this, I can remember us having it rear its ugly head a number of years ago on some 708 visions, Barco worked closely with us on this one but to no avail, again its down to the RGB amp (back end board).

    Barco went over to the Panny tube on the 'Black range' 808 so everyone automatically got the good 'cocktail version'.

    Paul, not sure but thought Mike only modded the Marquee Amps (neck boards) from the earlier Marquee, up to the ultra spec neck boards however you may be correct, he could well be doing barco mods.

    Remember Barco's units were not designed for home movies, it was mostly sim and presentation where that problem probably never happened.

    ps paul dropped you pm recently?........

    James
     
  17. Paul D

    Paul D
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    James,
    Sorry mate!
    I did read your PM, but was at work and wanted to reply when i had a bit more time to answer properly etc. :oops:
    I'm pleased to say my new business has really taken off, but has meant not much R and R!

    You may be right about MP and the Marquees, but i think he promised to do a Barco mod.
    But it sounds like you already know what the problem is!

    I've been trying to follow your secret gadget thread.....any news what it is yet? :D
     
  18. kalW

    kalW
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    Yup. Some extra info from a post some time ago:

    -------------------------
    What you are seeing is most likely luminescence peaking, a light streak running to the right of a light object on a darker background. A dark grey rather than black background looks the worst. Early 808 suffered quite badly from this but it was fixed on later ones. The fix relates to the tube backend boards mainly and later the FET on the RGB amps. You need R7621736 RGB amps with black FET’s and the later backend boards to more or less eliminate the problem. R7621735 RGB amps with black FET’s may also reduce the problem. Parts from a late 1998 projector and up should be correct.
    Be sure G2 voltages are correct, excessive voltages will make the problem worse. Only adjust with the projector fully warmed up. If the tubes are a little tired you may have to run G2 voltages up to the point were it highlights the peaking problem.
    Also make sure you are running V7.31 or V7.41 software as some timing parameters were changed. Go to Service and highlight Information then press enter to check software version. V7.31 and V7.41 are identical except V7.41 is the Iris 3 upgrade. Both have the small text menus and memory bank system
    -------------------------

    Here's a picture of the newer RGB amps:

    [​IMG]

    The Zenith Pro 1200x (basically a Barco Data 808s with LC'ed tubes - picture above) along with newer Barco's uses these newer RGB amps.

    Kal
     
  19. crteaman

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    Hi Kal,

    Bang on buddy, also for extra info, the Zenith pro 1200x was used as the Barco cine onyx, with a couple of minor addition's.

    james

    ps the Amps are rare, I had one set spare now sold and Henry had a spare set, which he sold to 'godfather'
     
  20. kalW

    kalW
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    Hi James!

    I did not know that! Thanks! I did know that the Cine 8 Onyx has (from looking at www.crtprojectors.co.uk): contrast modulation, custom colour filtered and corrected lenses and ultra high bandwidth RGB amplifiers. The Zenith has all those things as well (I put together some of the details on a major US/Canada reseller's web site here: http://www.curtpalme.com/Zenith1200.htm).

    The Cine 8 Onyx is also a full 120Mhz/110Khz machine, vs. 75Mhz/75Khz for the Zenith.

    Does the Cine 8 Onyx use the same HD215 lenses that are slightly softer in the corners?

    Any other major changes other then the built in Limo Pro (which nobody in their right mind with this projector should be using)?

    I'm supposed to be getting a basically brand new/unused one of these (less then 150 hours) fairly soon with so you can imagine my eagerness & curiosity. :)

    Kal
     
  21. crteaman

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    Hi Kal,

    No wonder you are keen to know, and I thought I may have been posting info that people may find boring....seems not good more info then, you got me on a subject I will talks los about here Kal due in part to owning a brand new onyx at one points a while back.

    Infact I sold and installed it for a guy in London who only last week came back to me, for a re-install due to moving house.

    Needless to say the first thing I told him to upgrade was to ditch the limo pro (set correctly far,far better then most give it credit for) and hook up a crystalio.

    I actually used my unit with limo pro,its very good with poor sources and uses some excellent filters, so was very good with my laserdiscs of which everyone knows I am still a big fan.

    Yup the onyx does indeed use the 215 lenses, I would not describe the corner focus as poor, amazing really as they have no edge focus (centre only) in fact they actually use less elements than most other lenses,which is a good thing.
    You could always get the corner focus within a hairs breadth,but never quite perfect but it is very close.

    I do however know of a lens upgrade for these, although very,very,very rare and very expesive indeed to buy new, but its all glass rather than the usual glass,acrylic mixture but sorry I am going off on a tangent here.

    The onyx of course used the high bandwidth RGB amps,(integral with the big heat sink on top) many Barco based units for example the later Runco 992 non ultra had these too but was simply limited to 75hz in software.

    So has your unit got these amps? the onyx was colour filtered, had the HDTV board, and contrast modulation as standard,oh and convergence on green, a must have in order to get the horozontal linearity correct.

    With the Panny tube plus liquid coupling it was a cracking unit, pretty much as sharp as they come, with just a couple of quirks, one being a lowish light output compared to some, i would say 72/80 screen isthe max here.

    Also it installs incredibly close, compared to all other Barco 808 units, from memory it installs around 15" plus closer,also the bolts which loosen the lenses are in a rather awkward and tricky position.

    Hope this helps thus far....

    james
     
  22. kalW

    kalW
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    Good to hear! I've heard many people trash the 215's but in the end I'd much rather have these lenses along with liquid coupling and coloured C-elements then a slightly 'sharper' air-coupled setup. The lack of an outside focus ring really threw me at first... never seen a PJ with only one focus ring!

    Yes it does - the picture I posted above was taken from a Zenith PRO 1200x. I'm assuming it's software limited in the same way, though bandwidth is also limited to 75Mhz so there must be something in the signal chain limiting this (as you can't really 'software limit' bandwidth).

    It's been very difficult to figure out exacty what boards the Zenith uses as the service manual doesn't mention the Barco board numbers so you have to simply look at the schematics and try to compare.

    I uploaded the service manual here in case anyone's curious: http://www.curtpalme.com/Zenith1200.htm

    No convergence on green in the Zenith. You can see here that the board is missing from in the convergence tray: (It would be on top of the bottom half of the top board)

    [​IMG]

    I run 96" wide but it's already going to be brighter then my current BG800 (that I'm happy with) so I don't see a problem. To each their own I suppose!

    Yes! This is actually something l'm quite looking forward to as it'll help give me some more headroom in my second row of seating which is on a riser. When I eventually upgrade to a 9" Barco things will get difficult however as that will install about 15" in the OTHER direction! :eek:

    Thanks James! Sorry for the off-topic posts ... didn't mean to hijack this thread...

    Kal
     
  23. crteaman

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    Kal, you are most welcome and not hi-jacking of any type, just glad I can help you guy's on my chosen subject.

    215 lenses were used on a few different units one being the Runco 852 series, which of course is a Zenith.
    These lenses actually list as HDTV lenses in Barco's parts list... I remember having my unit for a short while, when Henry (crtprojectors) sent me to Barco's HQ in Belgium on a buying trip and I came back with amongst many others, two almost unused G1209s.

    I remember Henry asking if I was interested in one so we set one up A1 in the workshop and I studied it for a long time to re-fresh my memory then went home to compare with my then new onyx........phew what a tough one Kal, boy what a close call in different ways.

    The difference in sharpness/beam spot size was vey close indeed,but believe it or not the onyx was a nose ahead, although lacking the light output of the 1209 so just losing out on depth and also background detail,having said that the onyx was using limo pro and the 1209 a stand alone scaler.

    Always wondered what the onyx would look like with a good scaler 'up it' looks like I will find out soon.

    Kal please note its most unlikely your bandwidth is limited, only your maximum scan rate, my buddy 'speedbird' here on this forum (sometimes) had one of a number of brand new D808s from Henry, over a year ago I am going to install it for him soon.

    This was originally destined for runco as a 992 (non ultra) but was a cancelled order, so they fitted Barco software and a black range case so as not to upset Runco....it too is limited to 75 Hz yet has high bandwidth amps....and Sony tubes, clearly Barco chose not to build two models,rather one was just limited in scan.(in fact my other buddy James also has one of these units)

    Must admit its a bit of a pain getting to the adjusters for the gun angle by shutting the unit down and popping the convergence tray...still although it may take several attempts its no big deal considering once its done it will be hanging there for months/nine inch upgrade :thumbsup:

    James
     
  24. kalW

    kalW
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    Thanks for the Cine8 Onyx vs. BG1209s comparison James! Interesting indeed. I would have assumed that a BG1209s (with new coloured c-elements) would have been considerably better then the Cine8. I find it all depends on source material as well. Upscaled NTSC (or PAL) doesn't benefit as much from the larger tubes then say wanting to do HD as 1080p. Very few PJ's have the bandwidth needed to do 1080p properly.

    The Zenith 1200 does seem to be bandwidth limited - the brochures and manuals all say 75Mhz max bandwidth (-3db) just like a 'regular' BD808s even though it has the higher bandwidth RGB output boards. The BG808s has 120Mhz, the BG1209s 135Mhz.

    The only way to be really sure I suppose would be to compare each of the boards in the signal path with a late model BG808s and BD808s and see where the differences are as it's not just the RGB output boards that could or would limit bandwidth I would imagine, no?

    Kal
     
  25. crteaman

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    Hi Kal

    I think its most unlikely to be the RGB amps limiting it, it will be scan rate limited in the controller by its firmware chip.

    Ps when I talk of the comparison between 1209 and 808 it only applied to a 82 onyx, not a non lc 808.Good comparison though as they had both done just 150 hours from new.

    So great unit, just limited light output, not a problem on my 'then' 80 screen, the guy who bought it off me had it on a 92" screen and we really had to push the contrast up a bit,I think Barco may have set the RGB driver board at a low level though, because as it was it had somewhat lower light output than a normal 808.

    Yet you could turn the contrast as high as you liked and it kept an ultra sharp focus all the way to the top! BTW 75hz should be enough for all of us, my ultra will run up to 152 khz, yet even upconverting 1080i to 1080p (or 1050p in my case) is only tickling my machine below its half way point. Although the Marquee chassis was designed to run at 100+ scan rate all day.

    Darn it got off the subject there, went all ultra there for a second :D

    James
     
  26. kalW

    kalW
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    Yup - the 75Khz is rarely the problem - most projectors out there that people consider scan high enough for their needs. It's the bandwith that's usually the limiting factor that creates a softer image especially for those wanting to run at 75Hz refresh (or 72Hz in NTSC land like me :) ).

    Kal
     

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