Calibrators- Michael TLV, Greg Loewen or anyone else- Blue Focus Questions

Discussion in 'Archived Threads 2001-2004' started by Phil L, Feb 25, 2003.

  1. Phil L

    Phil L Supporting Actor

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    I'm set to do the electrostatic (sp?) focus on my 51ws500 after a tech left the focus poor (CRT replacement-Flicker).

    I've read that blue should be slightly defocused? Is this right? Does this affect grayscale or make whites yellow?

    When I do this should my Picture setting be set to Max? Where should the user sharpness be at?

    Thanks
     
  2. David Abrams

    David Abrams Stunt Coordinator

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    Phil,

    When setting focus....first, make sure the set is not blooming by bringing the contrast and brightness into their linear operating range, then check for sharpness and set that where you do not see any added edge enhancement, finally perform the electrostatic focus.

    When performing electrostatic focus you will affect grayscale slightly - just keep this in mind. Be carefull not to touch the screen controls on the focus block, they are very sensitive, and do not defocus blue. Manufacturers defocus blue because its light output falls off first, by defocusing it they are using more surface area on the blue CRT and attaining a little more light output. Because you are bringing your set into its' linear operating range you will want to focus blue as best you can to achieve the sharpest picture possible.

    Best,

    David Abrams
    ISF Calibrationist
     
  3. Robert P. Jones

    Robert P. Jones Second Unit

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    I agree with everything David just stated. In fact, that's the best explanation I've seen yet as to why the blue focussing - and defocussing - does what it does. My compliments on his very succinct phraseology also.

    That said, I would like to emphasize that the blue focussing - or defocussing - inversely mimics the blue drive in the greyscale, and definitely DOES change the white balance.

    Today's newer CRTs don't need to be defocussed like the older ones did. They have what it takes already, and by and large most of the brands are not defocussed nowadays from the factory, for that reason. They are focussed as sharply as possible.

    But do not sideline the fact that the greyscale will change, if you electrostatically change the focussing of the blue. The whites will become blue-whiter or dingier, depending on what you do.

    If you don't have greyscale reference equipment, you are taking the efficacy of your factory-set greyscale in your hands by changing the blue focussing. If you think it sucks OOB, go ahead. If you think it is pretty healthy, I wouldn't touch it, on blue. They may have purposely defocussed it at the factory, and the greyscale may be dead on with it that way. You change that, and you may be ruining a perfectly good greyscale alignment.

    Blue is a fill color. Not a structure color, like red and green are, both of which need to be dead on and crystal clear. A slight amount of defocussing of blue, on the electrostatic, is not noticeable from any normal viewing distance.

    Mr Bob
     
  4. Phil L

    Phil L Supporting Actor

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  5. David Abrams

    David Abrams Stunt Coordinator

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    Mr. Bob,

    Thank you for you kind words. I, personally, have never seen a correct grayscale out of the box. Have you? This is very rare, focus has come pretty good an occasions but not as much as I would like to see it.

    Phil,

    To check to see where your contrast should be first set the brightness with the PLUGE pattern than go up to the screen and pull the contrast down to where the scan lines are the same size in the 100% window box as they are in the other boxes 80%, 60%, etc...Then bring the contrast to where you do not see the white box 100% start to turn yellow, this is where you are losing blue. Then you will have your contrast set pretty close - do not do a focus adjustment with it at 100!!

    As much as grayscale will change by adjusting the focus of the blue it will also change when focusing green and red. Where they are currently at is about where the set was adjusted to. I always focus all three CRTs to the best of their ability; however, I then finish up my calibration with grayscale adjustments and what not [​IMG] .

    Best of Luck,

    David Abrams
    ISF Calibrationist
     
  6. Gregg Loewen

    Gregg Loewen Video Standards Instructor, THX Ltd.
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    David, Bob, great answers!!

    David, yes Ive seen 1 (out of 350 plus sets) correct gray scale. It was on a new Mits RPTV with about 20 hours on it. Guaranteed that after 100 plus hours it would be significantly different.

    Regards

    Gregg
     
  7. MichaelFusick

    MichaelFusick Second Unit

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    This was a good post.

    Thanks to David and Mr. Bob for contributing.

    A good explanation of Blue defocus... best I have read [​IMG]
     
  8. MichaelFusick

    MichaelFusick Second Unit

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  9. Robert P. Jones

    Robert P. Jones Second Unit

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    David -

    Yes, I saw a correct greyscale OOB on a Toshiba about 5 years ago...

    Good suggestion, on checking the thickness of the scanlines at 100IRE vs. 80, 60, etc. That, and observing exactly where you are losing the blue is a great way to set it! I just leave the factory settings in there and run things at halfway and let it go at that. But yours is a more precise way of doing it.

    Maxing out the vertical height temporarily is another way to see the scanlines more clearly.

    Keep in mind, guys, that David is helping you set MAXIMUM limits. You may want to run it down from there a ways just to make your CRTs last longer, to prevent screenburn, for an even crisper picture...

    And if you are looking at your greyscale to see where it is at, don't use 100% IRE for trying to judge white, because as David mentioned, blue cannot keep up with red and green in the higher light level ranges, and starts to drop off well before they do. Causing dinginess in the whites at 100IRE. Use 80IRE for the whites on RPTVs. On plasmas, you may have to use 100IRE.

    I have seen red increase with red electrostatic changing of the red trimpot, but it was only once. Never green. Both may brighten and darken with trimpot adjustment, and thus affect greyscale, but neither of those colors affects it anywhere nearly as much as blue does.

    Don't use the AVIA patterns for greyscale. According to ISF they are slightly off. VE's, and the Sound and Vision disc, have accurate greyscale patterns.

    But don't use the VE patterns for geometry, they are bogus. Use AVIA's.


    Mr Bob
     
  10. Phil L

    Phil L Supporting Actor

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    I'd like to thank everyone who contributed to this tread. Your answers and comments were precise and helpful.

    I adjusted the electrostatic focus for all 3 guns this evening. I spent a lot of time researching/worrying about doing this but it was extremely easy, taking about 10 minutes. I then did some minor convergence work.

    Oddly red was the easiest to focus and green was the hardest but still seemed out of focus to me at the end.

    So I guess I need to do the manual focus as well but that's a problem for tomorrow.
     

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