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RGB Colour settings on FQ75

Discussion in 'TVs' started by Maidenman, Apr 13, 2004.

  1. Maidenman

    Maidenman
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    Morning

    I have had the Sony FQ75 for about 2 years and although pleased with it, I have never been blown away by the picture quality when watching DVD's.

    Anyway I brought my DVD player round to girlfriends house last night and quality on her Sony (28 inch not sure what model) and quality was far superior. The main thing I noticed was that you cannot change the colour mode on RGB on hers where on my TV you can adjust the colour.

    I do recall reading that you shouldn't be able to adjust the colour settings when viewing via RGB, is this a problem with my TV or does anyone know if there is a setting somewhere which switches RGB on or off. It doesn't say so in the manual and I have plugged the scart into AV1 (which is RGB).

    I bought it via unbeatable.co.uk and think they imported from Germany as the instructions were in German with a photocopy of English ones.

    Any comments?????
     
  2. Zacabeb

    Zacabeb
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    50Hz sets usually lead the RGB signal past a lot of circuitry and directly to the display stage in the set. With a raw RGB signal, you cannot adjust color saturation and in some sets not even things such as contrast or brightness. The latter depends on how much they cheat in order to get the RGB signal through the set.

    Some 50Hz sets and all 100Hz sets however convert RGB signals to YUV signals internally, where Y is black and white (mixed from certain amounts of red, green and blue), U is blue minus Y, and V is red minus Y. After being digitized in 100Hz sets, U and V are normally stored in a lower horizontal resolution than Y, like half or a quarter of it. This causes the color to smear compared to the raw RGB signal.

    With the color kept separate from brightness in the YUV signal, color saturation is adjusted simply by scaling U and V levels. Then the signal is converted back to RGB for display. When decoding a regular composite video signal, such as an analog broadcast, you also get a YUV signal, so once the RGB signal is converted to YUV, it takes the same path through the set as all other types of signals do once they've been decoded.

    100Hz sets generally don't have the crispness of 50Hz sets for several reasons, not just the lower color resolution, but also a number of other unfeatures such as Scan Velocity Modulation.

    A few (older, cheaper, or otherwise sad) TV's actually convert RGB signals to S-video internally. In that case, the RGB signal is converted to YUV, the U and V signals are modulated together onto a subcarrier in the PAL or NTSC system, and then immediately decoded back to YUV, having lost sharpness and precision the process. This is of course as incredibly stupid as it sounds, and probably only found in sets where the manufacturer has retrofitted RGB inputs to an existing design without a separate path for RGB.

    The S-video atrocity also has an interesting side-effect in some of said sets, by making RGB sources black-and-white if they are in 60Hz form. This happens if the S-video encoder encodes the color in the NTSC system, but the decoder cannot deal with NTSC and decode the color again. That might almost top the chart as the most stupid design approach in the history of color television. But, there is probably not a single TV set made which does not have any stupid solutions inside...
     
  3. Maidenman

    Maidenman
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    er um thanks.

    Although not sure what you said, so am I right in expecting that I can change colour settings due to the fact that the fq75 is a 100hz tv?
     
  4. Paul Atreides

    Paul Atreides
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    Yes.



    Could you expand on this please?
     

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