Gray Scale > Green Tint? Color decoder calibrated Correctly (Panny 47" HDTV, rp56)

Discussion in 'Archived Threads 2001-2004' started by Jon_H, Oct 30, 2001.

  1. Jon_H

    Jon_H Stunt Coordinator

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    Here is my current setup:
    Panasonic 47" HDTV
    Panasonic RP56 Progressive Scan DVD
    I recently applied the Red Push fix along with the SVM Mod and calibrated the color decoders on my set to be pretty good. The only thing is now everything has a green tint. I read somewhere that it is caused by the Gray Scale being off. Is this true? anyone know wheat settings in the Service manual are used to set the gray scale and how to set it up correctly. I have the Avia disc if that can be useful in setting this up. Any help would be greatly appreciated!
    Jon
     
  2. Guy Kuo

    Guy Kuo Supporting Actor

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    You may have fallen into the common and recurrent trap of newbies trying to correct their color decoders and mistakenly adjusting the grayscale controls cut (aka bias) and gain (aka drive). Those are the ones used to adjust gray scale, not the color decoder. The cut controls the amount of a primary at the dark end of the grayscale. The drive controls the amount of a primary at the bright end of the grayscale. It's pretty near impossible to set grayscale correctly without at least a good optical standard for comparison like a commercial optical comparator. It's much much easier and accurate to use a colorimeter. That's why grayscale adjustment is usually done by a professional who has the equipment. Most users simply don't have access.
    Time and time again I read about somebody fixing their "red push" by going into the service menus and turning down the red by turning down the red drive. DON'T DO THAT!!!! The drive controls alter the amount of red in everything including things which are not colored red. That's because the cut and drive controls change the underlying color of gray. If you "fix" the amount of red in red color objects by adjusting drive, you inherently ruin the grayscale.
    Color decoder adjustments are done using the decoder axis and gain controls. The names for these controls varies from set to set. One has to obtain the service manual to find out which control corresponds to the correct ones desired or else find someone who has the info for the same model. It's even possible for there to be no controls available for adjusting the color decoder. The point here is that it's important to adjust the color decoder controls instead of the grayscale controls.
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    Guy Kuo
    www.ovationsw.com
    Ovation Software, the Home of AVIA DVD
     
  3. Jon_H

    Jon_H Stunt Coordinator

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    Guy Kuo, thanks for the reply. In calibrating my color decoder I changed only the "Hue" and "Saturation" in my TV basic settings along with my axis and gain controls in the service menu (called something like R-YB and B-GB or some combination of those letters. These are the seting that I was told by a few sources on the forums on how to fix the Red Push, They also gave exact settings for these to fix the problem. (Link here I am assuming the the grey scale is just way off by default on my monitor resulting in the greeninsh tint when the color decoder is set properly. Does this sound right or possible? The Cuts and the Drive settings were never touched when settring the color decoder up. I may get the Set ISF calibrated if it comes to a point where I cant get rid of that green tint, but I would like to try first, of course by writing down all the original setting and being able to go back to them if neccesary. What would be the most feasable way for me to get a decent gray scale? are there and test patterns on Avia that can help me obtain a decent gray scale? You help is ver appreciated!
    Thanks
    Jon
     
  4. ThomasL

    ThomasL Supporting Actor

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    Jon,
    You should go into Avia and look for the grayscale patterns: the vertical ramp pattern and window patterns. The vertical ramp pattern shows the grayscale from 100 IRE to 10 IRE in vertical bands left to right. The Window patterns show 10 IRE to 100 IRE in windows in the middle of the screen. The latter is really the best way to take a look since it avoids any color variations that may occur across your set. Do you only see the green tint on darker colored areas on the screen...e.g. gray colored stone, pavement, shaded areas on walls, etc.? If you so, you may simply want to try and tick GCUT down a few notches depending on the scale used on your television (i.e. 1 tick out of 15 has a much more effect than 1 tick out of 100). Take a look at the 20 IRE window pattern and its matching vertical band on the ramp pattern. Make sure to write down all default settings and use the Avia patterns as you make adjustments. Guy is right that without a proper frame of reference and some tool to measure where you are in relation to that reference, it's very hard and probably impossible to get the grayscale set to D6500K.
    Finally, since you just fixed the red push, it may be that your eyes have not adjusted to the change and are seeing "green" everywhere. I guess my point here is don't alter GCUT too much to get rid of all the green since you'll be doing it at the expense of your overall grayscale.
    good luck,
    --tom
     
  5. Guy Kuo

    Guy Kuo Supporting Actor

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    Good. I think you did the color decoder correction appropriately. Most likely the grayscale on the set is off. The cautious GCUT advice advice given above should help. Write down those original settings for all the controls, not only the ones you intend to change. One slip of the finger and you've changed another control that you didn't write down.
    The real problem with setting grayscale without a reference to measure or look at is you end up going around in circles as your eyes keep fooling you as they adapt themselves. Typically I leave the green controls alone after setting green for perfect black level. Then I balance the red and blue guns around the fixed green gun. More green = less red & blue. Less green - more red & blue. Just remember to use the bright window patterns for examining the effect of gain controls and the dark window patterns for looking at cut controls. Get the two ends confused and you are guaranteed a mess.
    ------------------
    Guy Kuo
    www.ovationsw.com
    Ovation Software, the Home of AVIA DVD
     
  6. Jon_H

    Jon_H Stunt Coordinator

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    I noticed the green tint while watching a few movies, one inparticular movie was "Higher Learning" when Omar Epps was wearing what I think should have been a gray sweatshirt looked greenish to me, i didnt think it looked right. Plus after I calibrated the set and my Girlfriend Came over, the first thing she said was why the picture looked green. Thanks for the advice and tips guys. Im gonna try those mods with those test patterns, if I cant get it looking decent I will just get it ISF'd. I would like to take that money that I could get it ISF'd with and put it towards a HDTV Tuner. We'll see. Thanks
    Jon
     
  7. Carlo Medina

    Carlo Medina Executive Producer

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    As I said in your other thread, you will probably need the ISF'ing to get rid of it. My PT-47 was way too green until Michael TLV took care of it. In fact, although my DVDs look perfect (progressive) my cable still looks a tiny bit greenish, but I think that is due to how it handles cable signals. When I switch my DVD player to interlaced, it does not appear greenish.
     
  8. ThomasL

    ThomasL Supporting Actor

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    Jon,
    I had/have the same problem with a analog Toshiba set (27A40). I mostly saw too much green in darker scenes on dvds. Since this tv has a fairly balanced color decoder as low end sets go, part of it was simply my eyes seeing a more balanced color spectrum but even after some period of adjustment, my eyes couldn't shake it so I went in to the service mode and looked at the Avia patterns. I could see a slight green tint on the 20 IRE window pattern so I ticked down GCUT a few notches and ticked up BCUT a few notches which gave me something my eyes told me looked more neutral gray. I have no way of telling if this is true since I have no reference points. For this set, it would cost as much as the set to have it ISF'ed :)
    It is true, if you fiddle with things long enough, your eyes will "compensate" and one set of settings that looked fine won't look fine a few hours later or the next night when you look at them again, so make sure to go back and look at things again after tweaking. In addition, make sure to make adjustments in the lighting environment you watch dvds in.
    hope this helps,
    --tom
     
  9. JohnnyG

    JohnnyG Screenwriter

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    Maybe you have taken R-Y_A down too far. On the earlier sets I calibrated, zero was the proper level, but on newer sets, it's more like 3-5.
    The 'correct' way to adjust the decoder is described by Guy Kuo here http://www.hometheaterforum.com/uub/...ML/008816.html
    [Edited last by JohnnyG on October 30, 2001 at 03:39 PM]
     

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