DIY Calibrators Please Read - Grayscale is NOT Color Decoding

Discussion in 'Displays' started by Guy Kuo, Mar 19, 2002.

  1. Guy Kuo

    Guy Kuo Supporting Actor

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    If you are new to working inside a service menu, please see the following and avoid a very common, recurrent pitfall.
    http://www.hometheaterforum.com/htf/...librators.html
    Note: I'd like to keep the commentary in the above linked thread rather than here so we don't have two identical threads running. It would be nice to keep this tickler thread also present so the maximal number of affected people get a chance to get the message. It keep seeing this problem happening and hope to make some sort of dent in it. I'd put it in home theater basics, but it's probably too deep for newbies. This is a problem that happens when one learns enough to be dangerous but not fully put 2 + 2 together.
     
  2. Jay Mitchosky

    Jay Mitchosky Producer

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  3. Bill Will

    Bill Will Screenwriter

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    The new Sound & Vision Mag. has a nice article explaining all about ISF & calibration in nice simple terms, at least to me anyway [​IMG]
     
  4. Ted Lee

    Ted Lee Lead Actor

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    guy - isn't there an 'advanced' section in the newbie thread? it'd be perfect for that section...
     
  5. Guy Kuo

    Guy Kuo Supporting Actor

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    Looks like this is working. I have not run across any "helpful" go fix red push by adjusting the red cut and gain controls comments for some time. That's a lot fewer winces and grimaces to wrinkle my face.
     
  6. James Zos

    James Zos Supporting Actor

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    If you can't fix red push by adjusting the grayscale, am I correct in assuming you can't fix a greenish hue by adjusting the grayscale?

    I ask this question because I have a very slight greenish hue to the picture on my TV, and a shop I talked to suggested it could be fixed by adjusting the grayscale. They actually used the terms green gun and grayscale to mean the same thing. Are they the same? Can I fix my problem by adjusting the graygun?
     
  7. Guy Kuo

    Guy Kuo Supporting Actor

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    If the greenish hue is present in a black and white picture then yes, you can fix it in grayscale because it would be a problem in grayscale. On the other hand, if black and white picture's don't have that greenish hue, it is something which is happening in the colorization. You MUST look for grayscale problems by using images which inherently have no color (black and white). Otherwise it is impossible to tell where the problem lies.
    I do hope you weren't using Matrix as the test image. [​IMG]
     
  8. James Zos

    James Zos Supporting Actor

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    Uhh ... I hope I don't make myself look really stupid with this answer. No, I wasn't using The Matrix as my test image - but the greenish hue IS most prominent with The Matrix ... Is it supposed to look like that?

    Even if it is, I have the problem, to a lesser degree, with other DVDs. Where images are supposed to be black, I can actually see green pixels if I look really close at the screen.

    Nevermind - I did a search on "Matrix" and "green" and found a thread where this was discussed. It was deliberately tinted green. Glad my TV is not THAT bad. But I still have a problem with green hue in other DVDs as well. I turned the color all the way down and looked at a black and white test pattern and there WAS some green in it. So I think it is a grayscale problem after all. Just got to take into my local shop (which I know nothing about) and take my chances ...
     
  9. AllenD

    AllenD Second Unit

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    James,

    If you let us know where you're from, maybe someone can suggest a reputable dealer.
     
  10. James Zos

    James Zos Supporting Actor

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    Thanks for the suggestion, AllenD. I'm not from here, but I'm living in Northern California at the moment, in Mendocino County. I may be moving to Portland, Oregon though, in the not too distant future.
     
  11. Michael_V

    Michael_V Second Unit

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    I would love to decrease the red push on my new 48 in JVC HDTV. Any ideas how to do this in the service menu?

    Mike
     
  12. Robert P. Jones

    Robert P. Jones Second Unit

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    I live in the SF Bay Area, CA, and travel every couple of months to Portland Oregon.

    I'm not exactly sure how far Mendocino is from East Bay, but I have been requested to drive from as far away as Sacramento and Modesto. A few weeks ago I was paid to drive up to Redding for a calibration on a 73" Mit. I'm sure Mendocino can't be TOO far away.

    Give me a call and we can discuss a calibration for your set, if you'd like.

    Mr Bob
     
  13. Robert P. Jones

    Robert P. Jones Second Unit

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    Michael_V -

    Are you sure you want to do red push, and that you are not talking about greyscale? Greyscale is purely a b/w thing, push purely a color decoder thing.

    I haven't cal'd a JVC HDready yet, but the red push registers you're looking for are usually something like R-YR, R-YB, G-YR, and G-YB, tho the Pannys use completely different kinds of abbreviations. Those stated are what Mit and Sony use.

    Mr Bob
     
  14. Michael_V

    Michael_V Second Unit

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    Mr Bob,

    Would an inaccurate gray scale give elevated reds in the color decoder check portion of AVIA? The initial values for my set were +25% for reds with blue at -20% or so. My impression was that gray scale could not correct this kind of discrepancy. Having said that, the gray scale is visibly off on my set, with a pink hue to the higher IREs. I fiddled around in the service menu and found the DRVs and CUTs and pulled back the RDRV a bit (to correct the gray scale, not the red push), with some improvement, though a non-HT neighbor came by yesterday, looked at the picture, and commented on the pinkish hue to the image.

    I do believe that, with tweaking, this set will probably be able to produce a fairly good picture, though there are other issues (namely the imperfect upconversion, spotty initial QA reported, and soft picture with progressive source material) that prevent me from investing much more time or energy into it.
     
  15. Robert P. Jones

    Robert P. Jones Second Unit

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    You're on the right track - pink in the whites is a sign of greyscale, not red push.

    The color differentiations are affected very little by the greyscale - which is luminance only info - not chrominance, which is the color differentiation info. Colors are created in an RGB system by themselves plus the variable lack of the opposing colors.

    The values mentioned do indicate red push, and the pinkishness in the whites indicates greyscale error, both of which are prevalent in many new, OOB units.

    Are you interested in an Image Perfection calibration? If so, I can address those issues and many more, and deliver you a superfine lookin' set. Hopefully the JVC brand has included the registers I mentioned before. If not, other things can be done to cure the red push issue, on component inputs. The greyscale is a no-brainer for me and my ISF equipment.

    Just fly me in yourself, or get some fellow afficianados to go in with you and have me in for a calibration tour. I was just flown to New Jersey from CA, and it was only a 5 hour flight.

    Mr Bob
     
  16. Michael_V

    Michael_V Second Unit

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    Mr Bob,

    Thanks for the offer. I would certainly take you up on an isf-calibration if (1) I were keeping this set (I am not) and (2) I weren't moving overseas (to Okinawa) at the end of the month. I am inclined to include the cost of calibration in whatever set I do end up buying, though (the subject of a future post: what 43-55 inch 16x9 HDTV in the $2-3K price range to you recommend?).

    Thanks again.

    Mike
     
  17. Robert P. Jones

    Robert P. Jones Second Unit

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    My top 5 brands are Mit, Sony, Toshiba, Panasonic and Pioneer; can't make any comments about the pricing, because I don't know much about that.

    I recently did a Philips-based 55" Marantz, and was quite impressed, since the last Philips I did had a convergence system that did not allow for high precision, and would curl at corners at the drop of a hat. This one co-operated grandly, and I was able to obtain the razor-sharpness I like in the convergence op.

    So I would have to include the Marantz in there now, also.

    The manufacturer told me it was absolutely impossible to efficiently do the 55" pic geometry correctly without using the 55" template, so I bought one from them before doing the job, but after finding I needed to correct the geometry anyway, because the template did not allow for 4.5% overscan via the AVIA overscan and circlehatch grids, I don't think I'll be using it again.

    The main reason was that on the Philips based units, you cannot get the service menu to show you the signal source pic you're trying to look at, for geometry purposes.

    That's not enough for me, when you compare the known good AVIA geometry patterns with and without the use of the factory template - which matches up exactly ONLY with the internal service menu grid lines - and find they are not the same. I used the template - which also accurately indicates dead center, but dead center is also easily obtainable thru 2 strings attached at the corners and crossing each other in the middle - and then had to correct the template's info after obeserving that it did not match the AVIA grid. Amazingly enough, it UNDERSCANNED the screen, and I had to expand it in the overscan direction on this unit, to get it to match up with the AVIA at 4.5%. Directly opposite from what I normally find in OOB RPTVs. 1-2% overscan is too small a pic to be able to rely on not having certain stations across the country showing a side here or there, or top or bottom.

    It was not expensive, but ordering and depending on the grid did delay the job by a week. Next time I will just mechanically go in and out of the service menu more times, like I had to do anyway, this time.

    I believe all of the above also use 7" guns - Zenith and Philips use 9" guns in their 65" units, and of course the Mit uses that in their 73" unit. But again, I question the convergence system used by both Zenith and Philips, having had problems with it in the past.

    The 65" Hitachi I cal'd recently wound up with a picture that I swear couldn't have had more than a 5" gun; after all my known and well documented patience as a calibrator, its pic still didn't measure up to what I've always been able to get from those other brands mentioned above, in terms of image crispness. The customer was completely happy with it when I was finished with it, but I was not, and would not have had it for my own TV. Which is a 65" Panny, which turned out ultra excellent, and which I couldn't be happier with.

    But I do Hitachis very infrequently - quite rarely, AAMOF. Perhaps the next one will surprise me in the other direction.

    Mr Bob
     
  18. Mark Walker

    Mark Walker Cinematographer
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    Mr Bob-
    I noticed that you mentioned you come to Portland,
    Oregon every few months.
    Would you be intersted in calibrating my Toshiba 36HFX71?
    I realize it isn't a "big screen" by most standards, but
    I would love to have it professionally calibrated by an ISF
    certified person like yourself.
    I live in Wilsonville, which is a 15-20 minute drive from
    downtown Portland, depending on traffic.
    Let me know if you'd be interested, and what a price
    estimate would be.
    Mark Walker
    dvdfilms@yahoo.com
     
  19. Robert P. Jones

    Robert P. Jones Second Unit

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    Love to. email me with your phone number, etc., or give me a call.

    The big directviews usually run from $300-450 plus travel, depending on things like whether they have multiple scanrates and as such are both HDready along with NTSC capable, do or do not have geometry and/or convergence capacities, etc.

    The smaller ones, where greyscale on one scanrate is the only op desired, can be as low as $250 plus travel.

    Mr Bob
     
  20. Guy Kuo

    Guy Kuo Supporting Actor

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    As this thread has drifted off the purpose for being fixed at the top of the list, I think it is time to let it drift into the nether world.
     

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