Avia Color Decoder Check: Is It The Whole Story?

Discussion in 'Archived Threads 2001-2004' started by Brent Hutto, Aug 20, 2002.

  1. Brent Hutto

    Brent Hutto Supporting Actor

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    My new 36XBR800 produces a very nice picture with both my old RV31 and the new RP82 I bought along with the new TV. However, with the RP82 the colors are defintely more saturated and there is an objectionable excess amount of red that wasn't there with the RV31.

    So I've worked with the user-mode settings along with R-YR and R-YB (to produce less red) and G-YR and G-YB (to produce more green) in the service mode in order to flatten out the color differences. Based on the Avia Color Decoder Check, I can get Red and Blue to 0% and, depending on the G-YB setting, somewhere around 0% to -5% Green.

    Contrast is adjusted using the regular Avia moving black bars (one just visible, the other just barely invisible) with the RP82 set to "Darker" blacks. White level is set near the middle of its range since I can't really get a definitive setting from Avia for this parameter. Certainly no blooming and probably erring on the side of less-bright whites. I am using the "Warm" color temperature and "Pro" picture mode as the basis for all these settings.

    With this setup, I think I see some green in the yellow elements of most scenes on DVD and skin tones (faces) are not satisfactory. Also, the yellow bar on the Avia Split Color Bars (with 75% gray) looks pretty sickly to me. I can get more pleasing people colors by moving the G-YR and G-YB almost back to their factory default settings, but then I end up with +5% Red, -5% Blue and between -5% and -10% Green on the Color Decoder Check.

    So my question is the extent to which zeroing everything on the Color Decoder Check is the be-all and end-all of color fidelity. In theory, that should induce the TV to show me pretty much what the moviemaker intended, right? Somehow, I don't think Peter Jackson wants Gandalf to look like he's been eating carrots or Frodo to look like he is seasick. Am I paying too much heed to Avia? Should I just start from what Avia considers color-neutral and then tweak it by the seat of my pants to get correct skin tones?

    A related problem is that these same settings mess up the picture on other (non-composite) inputs (tuner, s-video) so I have to switch to the "Movie" mode and bump the "Hue" slider over toward the red a bit to make skin tones even close to correct on cable TV and satellite programming. That makes me think that the RP82 itself is pushing red or eliminating green to some extent.

    Let me say this, though. With the settings I arrived at via Avia (no pun intended) there are certain scenes that look much, much better than they do on the old DVD player. For instance, at the beginning of Chapter 9 on Fellowship of the Ring when the mane of Gandalf's horse is briefly backlighted by the sun, the color is a wonderful auburn rather than the somewhat dull brick red that I get with a non-progressive input and/or the service mode settings in their factory defaults. Gorgeous.
     
  2. ThomasL

    ThomasL Supporting Actor

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    Brent, have you adjusted the underlying grayscale using a color analyzer? I would think you'd want to get the grayscale right first before fine tweaking the color decoder. Even on the Warm setting, it doesn't mean that it is close to 6500K.

    cheers,


    --tom
     
  3. Brent Hutto

    Brent Hutto Supporting Actor

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    Tom,

    No, I don't have any way to evaluate the grayscale. It's my understanding that the only way to do that is to hire someone with a pretty expensive machine to measure it and that doesn't seem like something I want to spend a bunch of money on.

    So you're saying that unless grayscale is pretty close to reference color temperature, then 0%/0%/0% on the color decoder check isn't necessarily the optimum setting, right?

    If so, then maybe a reasonable path to take is start from 0%/0%/0% with whatever grayscale "Warm" produces on my TV and then play with G-YR and G-YB until faces look "natural" to my eye. That's what I'm inclined to do anyway, so maybe it would be for the best (absent a few hundred bucks worth of specialized calibration).
     
  4. John Royster

    John Royster Screenwriter

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    The color Avia filters are not perfect and I "think" they do leak a little green/blue.

    With RPTVs you can cover up certain guns for total accuracy. Maybe you can via a service menu display all red, blue, green.

    If you want to get your color decoder spot on then you can use the blue bars, red bars and green bars with their respective filters to adjust each color. then use the color decoder check as a final measurement.
     
  5. Brent Hutto

    Brent Hutto Supporting Actor

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    John,

    Your reply along with Tom's induced me to do a more thorough search of the archives. Mr. Kuo also suggested the iterative blue-red-green approach you mention here. That sounds like something I can handle.

    Per another previous thread, I'll first look at some of the grayscale test patterns and make sure there's nothing so wrong there that I can see it by eyeball. Hopefully, Sony's "Warm" grayscale is in the ballpark and cycling a couple of times through blue-red-green bars will get me to the point I can forget Avia and just watch movies...
     
  6. ThomasL

    ThomasL Supporting Actor

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    Brent, grayscale and color decoding are independent but the two come together to form the picture you see on the screen. Think of the grayscale as the underlying canvas and the color decoder as the paint going onto the canvas. If the grayscale is off, then colors may still seem "off" even with an accurate color decoder. For example, so many sets have a very hot grayscale (blueish) that in order to balance out fleshtones, an overemphasis of red in the color decoder is done. If one was to re-align the color decoder before reigning in the grayscale then most likely fleshtones would look sickly looking. I think many in the forum would say that if you've spent a good deal on an HDTV-ready set that you should try and save the money for an ISF calibration to bring out the set's best possible image for HD and dvd viewing. Short of that, I'd definitely check the Avia grayscale patterns and see how they look. If you can see a tint to them then you definitely need adjustment. Usually one can do an "in the ballpark" tweaking using their eyeballs, but I'd recommend if you do this that you do it over several sessions since the first time your eyes are very liable to over compensate for the tint that they see. I think after that, that tweaking the color decoder to where your eyes are comfortable with the colors is the best thing. It is true that Avia is not 100 percent completely accurate especially when using the filters. Since your set is a direct view set, I don't think there will be a way for you to shut off each individual color "gun" (like with an RPTV), but it's worth the investigation.

    good luck,


    --tom
     
  7. Brent Hutto

    Brent Hutto Supporting Actor

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    I went through the grayscale patterns on Avia. Of the three color temperature settings, either "Warm" or "Neutral" are closest to what I'd call white. With an overall white or gray field, "Warm" looks the most like white or gray. With the vertical or horizontal 10 IRE bars, the 30 IRE one might have a slightly plum colored or dark purpleish cast. The 20 IRE and 10 IRE ones look basically black. With the 0-100 IRE ramp patterns, no part of the picture looks to be a different color than the rest.

    On the "Neutral" setting, the darker IRE levels look neutral gray but there starts to appear a bluish cast at the 70-100 IRE end of the scale. At any rate, I find the "Neutral" and "Cool" settings unpleasant to look at, so I didn't seriously consider using them.

    I'll try it again another day and see if I have the same impression.
     
  8. Brent Hutto

    Brent Hutto Supporting Actor

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    Once I determined that the "Warm" color temperature was in the ballpark of a good grayscale, I use the iterative Blue Bars, Red Bars, Green Bars approach to set "Color", "Hue", R-YR, R-YB, G-YR and G-YB. This was after I had set "Picture" and "Brightness" according the usual Avia basic patterns.

    Here's what I ended up with:

    R-YR=14 (default is 8)
    R-YB=13 (default is 9)
    G-YR=6 (default is 9)
    G-YB=2 (default is 6)

    Mode=Pro

    Picture=32/64 clicks
    Brightness=33/64 clicks
    Color=35/64 clicks
    Hue=Dead Center
    Sharpness=31/64 clicks
    Color Temp=Warm
    ClearEdge VM=Off

    So for the user-mode settings, the only thing much different than the Pro mode defaults is that "Color" is turned up three clicks and the "Color Temp" is set to "Warm". White level, black level and sharpness are within a click or two of the defaults.

    I tried looking at various scenes from Fellowship of the Ring and this is the best calibration pass yet, by far. Both bright and dim scenes are sharp and clear with consistent colors. I've written down these settings and they will probably become my default calibration for DVD viewing.

    I don't know what's so different now, but the tuner and s-video inputs don't seem to have any green cast. I prefer the "Movie" setting for those inputs but either my Pro mode calibration settings or the Movie mode defaults produce a good-looking picture from any source.

    Short of paying someone with test equipment for a calibration, I don't think I'll do much better than this. Thanks to everyone who helped out. Hopefully, this thread will help someone down the road if they're setting up a 36XBR800/RP82 combination.
     
  9. Brent Hutto

    Brent Hutto Supporting Actor

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    One final note, per the title of this topic...

    FWIW, the final calibration that I'm satisfied with gives these levels on the Avia Color Decoder Check:

    0% Red, 0% Green, -5% Blue.
     
  10. Gregg Loewen

    Gregg Loewen Video Standards Instructor, THX Ltd.
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    Looks like you now have it nailed. Please continue posting if you have additional questions.

    When adjusting the color decoder use the flashing Avia color bars. You will have to cycle through Blue, Red, and green at least twice if not 3 times to get them close.

    Remember that if they are all within 10% of the avia test pattern, then you are all set. There is always some interplay / interpretation when dealing with anything "eyeballed". Also, the color filters themself introduce error.

    Regards
    Gregg
     
  11. Brent Hutto

    Brent Hutto Supporting Actor

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    Gregg,

    Thanks for the suggestions and the feedback. I made three loops through the process but only the first two resulted in any changes.

    The first pass, all four service mode settings changed and then the "Color" user control had to change.

    The second time through, I nudged R-YB one unit and then I believe both G-YR and G-YB changed. At that point, the blue bars were still fine as they were.

    Once more through the green bars and red bars. I tried moving each control up and down one level which confirmed that I was at at least a local minimum of blinking. I ended up with all of them in the same spot as at the end of the second pass.

    One last observation. I found that the settings of the four service mode controls and the "Color" user mode control were highly sensitive to the black level ("Brightness") setting but much less so to white level ("Picture"). So I think I could move "Picture" up and down a bit without changing the calibration, if I needed to for some reason.
     

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