Why is VSM bad?

Discussion in 'Displays' started by Brendan M., Nov 27, 2002.

  1. Brendan M.

    Brendan M. Extra

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    In reading these forums it seems that the universal opinion is to disable VSM (velocity scan modulation) whenever possible.

    I know that VSM is supposed to sharpen the edges on images, and to my thinking a sharper image is a better image (within reason) no?

    I've found a description of VSM online as the following -"this TV feature creates sharp transitions between objects on your TV screen and improves overall clarity. If you can imagine a big letter E in white on a totally black screen, a set with V-Scan will show crisp, sharp edges on the letter while a set without V-scan will gradually transition from black to gray to white with a much softer look."

    Now, I understand the whole 'faithfully recreating images' philosophy, and if something is artificially sharpened when it shouldn't be, then that's not good, but...my question is: on the whole, why is leaving VSM on such a bad thing? Can anyone provide an example of when VSM has caused a problem?
     
  2. Joshua L

    Joshua L Agent

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    Woops...wrong thread [​IMG]
     
  3. Frank@N

    [email protected] Screenwriter

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    Well, I'm no expert. But I've read that using VMS shortens tube life...

    I've got a direct-view WEGA with 3 VMS settings, if I recall correctly.

    I used to use the lowest VMS setting because I thought it enhanced picture quality (this was determined while viewing moving images, kinda tricky).

    Later I was using the free THX calibration tool which comes on some DVDS and found that VMS was blurring fine details (this was determined using still test images).

    Specifically, I was looking at some of the fine lettering at the bottom of some of the test images.

    I figured that if I could make this small text as clear as possible that other fine picture details would be better resolved as well.

    So, I'm running with VMS off and Sharpness at a fairly low level.
     
  4. Matthew Todd

    Matthew Todd Second Unit

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    Hi Brendan,

    Someone will probably come in and give a better example, but if you have Video Essentials or Avia and you pull up a needle pulse pattern (I think that's the one -- It is a thin vertical line on a contrasting background -- I think black on white, maybe visa versa) you can see the effect of VSM.

    Without VSM you see a thin vertical line. With VSM you get a much fatter line.

    I hadn't heard the description of what you just gave before, but from that it almost seems as if VSM takes the gray portion and makes it all the color of the line. You end up with a sharper transition, but the fine detail of the thin line is gone.
     
  5. Jan Strnad

    Jan Strnad Screenwriter

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  6. Jesse Skeen

    Jesse Skeen Producer

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    "Sharper" does NOT mean "Better"! When my TV had it on everything looked like someone had drawn outlines around everything, and it was usually hard to read any text that was on the screen. I finally went inside and disconnected it and everything looks a LOT better. (Turning up the sharpness control is also not a good thing; on mine I have it all the way down!)
     
  7. elMalloc

    elMalloc Supporting Actor

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    view the transitioned image as it's supposed to be.
    that's the whole reason of goign 16x9, same applies to VSM.
    -ElmO[​IMG] [​IMG]
     
  8. Vader

    Vader Supporting Actor

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  9. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Greetings

    Look at the post date ... 5 years ago ... I don't think they care anymore?

    Regards
     
  10. Vader

    Vader Supporting Actor

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    I know.... I just never heard that using VSM had any effect on tube life...
     
  11. ChrisWiggles

    ChrisWiggles Producer

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    I doubt it really matters much. But I guess since VSM is increasing intensity in the brightest parts of the image you could be at faster risk for burn-in issues with still images with high-contrast boundaries, but otherwise I'd expect the effects to be spread out across the screen and fairly negligible.

    In any case, it would be extremely minimal, and the folks who are in torch mode with VSM full blast probably wouldn't ever know or care about tube wear anyway, so...
     

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