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50Hz vs 100Hz

Discussion in 'Televisions' started by stevejknight, Jan 2, 2003.

  1. stevejknight

    stevejknight
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    I have looked at the 2 types of sets 100hz and 50hz and have not seen a lot of difference in the picture.
    I have heard of strobe affect with fast moving action on 100hz sets.
    What are the real issues and benefits of both frequencies.
    Is there some further technology that will be available in the future that will require 100hz sets?
     
  2. LV426

    LV426
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    100hz sets are not likely ever to be a requirement as such.

    The fundamental principle behind 100hz TVs is that some people (more than others) are sensitive to the low 50hz refresh rate exhibited by standard TVs. All PAL TV signals are inherently 50hz in nature.

    What 100hz TVs do (some in different and more or less intrusive ways than others) is to take each incoming frame (which lasts for 1/25 of a second) and store it in a memory. Then, it is displayed twice. Thus doubling the refresh rate. And reducing the visibility of the refresh - for those who are sensitive to it.

    As a side-effect, however, the introduction of additional processing to the signal (converting it to a digital form for memory storage) can have adverse effects on the picture - smearing is often mentioned.
     
  3. paperclip21

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    If you've seen 50Hz and 100Hz side by side, and can't see the difference, then buy whichever suits you.

    When I saw the Sony LS35 (50Hz) and LS60 (100Hz) sets side by side, the difference to me was massive - but I'm very sensitive to flicker.

    The LS60 has the most simple 100Hz possible - it stores frames and displays them more quickly - it doesn't do any additional processing.

    So it stores two frames A and B and displays AABB - so if you have a moving line, you'll see

    _ _ _ _
    _ _ _ _
    ooooo_ _ _ _
    ooooo_ _ _ _


    Your brain expects smooth movement, i.e.

    _ _ _ _
    oooo_ _ _ _
    oooooooo_ _ _ _
    ooooooooooo_ _ _ _


    so the picture will appear to judder.

    This judder is why the simple AABB 100Hz was thought to be inadequate - leading to all sorts of picture processing to attempt to interpolate movement between the displayed frames.

    I can't comment on how well the latest of these techniques work, but I suspect at least some of them are complete crap - hence the usual recommendation is to turn all picture processing off.

    I've got a Sony 32LS60 100Hz set - you can tell because scrolling horizontal text looks bad -- unreadable really.

    However, I don't spend much time looking at end credits, so it's not important to me...
     
  4. nutball

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    Is this flicker worse than the picture displayed at 50Hz? If so, why? It doesn't really make sense.
     
  5. paperclip21

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    No, the flicker is reduced with the 100Hz set, because the screen is being refreshed more frequently. The picture is therefore easier on the eye, but you do get the judder (actually, it's more like blurring) as a side effect.

    On fast moving horizontal credits, particularly thin white text, which is common at the moment at the end of a load of BBC programmes, the letters look like blurry, double images as they move across the screen. On a 50Hz set this text would obviously look normal.

    Must emphasize again that this is a Sony LS60, which has no extra processing to try and reduce this characteristic feature of AABB 100Hz.
     
  6. roadtorode

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    I have read that the value of 100hz is limited below 32", but I can't justify this statement; but what I can confirm is that sky digital can look better on a 50hz set than a 100hz set but I understand this is sky's fault (low bit rates etc) and that the 100 hz set is essentially revealing a weakness is the transmission signal.

    I have an 28" LS60 (100Hz), which is great for RGB DVD, very fine for old VHS, very good for RF signals and ok for SKY now I have got the picture settings optimized...

    But try before you buy using your most common source...
     
  7. Nello

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    if you buy a 100hz set does it have the option to switch between 50hz or 100hz or does it always refresh at the maximum rate?
     
  8. GaryB

    GaryB
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    All the 100Hz sets I've seen refresh at only 100Hz. In answer to the original question, I'd recommend an extended demo before you make a decision. The side effects of 100Hz processing are subjective and most people either love 'em or hate 'em (I hate 'em). Typically you will see the strobing effects described above, a stationary "grain" that is noticeable on fine moving backgrounds such as football and pixellisation on fast moving scenes. They can give some odd effects when watching old black and white films. The strange thing is that two people looking at the same set can see the effects to different degrees. Must be something to do with the way our brains process the information I guess.
     
  9. Ian Maurice

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  10. roadtorode

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    Some sets are switchable; eg SONY 75FQ and new 80FQ
     

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