horizontal resol pixel vs test pattern

Discussion in 'Archived Threads 2001-2004' started by ross ish, Mar 9, 2003.

  1. ross ish

    ross ish Stunt Coordinator

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    I noticed that Panny RPTV list their resolution at 850 lines. I questioned Panny tech if their sets were downconverting HDTV signals to 850 lines. I wanted to clarify if their 850 lines is the same as another mfg claim of 1200 lines. Here is the reply from Panny:

    "The whole issue of resolution is a numbers game. It all depends on what is measured, and how. For example, you could claim horizontal resolution based on the number of pixels, on the bandwidth of the video amplifiers, or on a special resolution pattern (our method).

    Since there is no standard way of measuring resolution in the industry, manufacturers can claim whatever benefits them the most. Therefore, it is up to you the customer to view the sets in person. "

    Is there any conversion between test pattern resolution and pixel horizontal resolution...in other words, is the 850 lines using the special resolution pattern equivalent to what resolution using the pixel count?
     
  2. Allan Jayne

    Allan Jayne Cinematographer

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    The TV is probably not downconverting, rather due to less than perfect electronics and picture tube it is blurring the picture a bit. (Some TV sets do some digital processing of the HDTV 1080i signal that does result in horizontal downconverting.)

    The TV is still accepting and attempting 1080i which is 1920 pixels all the way across by 1080 scan lines high. However by the time the video gets to the picture tube, the smallest spot achievable is such that two separate spots with a distinguishable dark gap in between cannot be made to occupy a span less than 3/850'th of the screen height (using truthful and technically correct descriptions). You can think of it roughly as the smallest spot achievable is 1/850'th the screen height in diameter.

    If a 4:3 screen TV truthfully has 850 lines of horizontal resolution per (distance across equal to the) picture height, it is said to have almost 1200 (1133) lines all the way across.

    To me the standard way of measuring resolution of a TV set ought to be to view a test pattern.

    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     
  3. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Greetings

    If Panasonic measures resolution based on a resolution chart as you have quoted, then the 850 line number is 850 lines per picture height.

    850 lines based on a square. Of course since the TV shape is not a square ... you multiply it by the aspect ratio.

    Now here it gets tricky ... do you multiply it by 1.78 or 1.33? With a 16:9 set, you'd think 1.78 ... but actually the number is 1.33 since the crt's are the same as those found in 4:3 sets.

    1.33 x 850 = 1130 lines or pixels from left to right.

    This is actually consistent with what I am seeing in the field. Pioneer uses 1200 to 1300 lines left to right for their sets.

    Regards
     
  4. ross ish

    ross ish Stunt Coordinator

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    Thanks, this really clears things up. I noticed that Panasonic has taken the horizontal resolution off of its product description...for a newbie their 850 lines appear to be inferior to anothers 1200 line claim when in fact they are the same. Another reason to have mfg standardize measurement specs.
     
  5. SeanA

    SeanA Second Unit

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    This is an interesting conversation. I had been puzzled by this horizontal resolution issue as well. It seemed to be all over the place, depending on the manufacturer, and just did not make sense. And than some manufacturers just don't divulge this information. I just contacted Sony to try to find out the horizontal resolution for my KV-34XBR800, but all I got back was some canned reply defining horizontal resolution... no hard numbers.

    In theory, since an HD pixel is suppose to be "square", I would think the horizontal resolution would have to match the vertical resolution when measuring over the same distance (height and width).
     
  6. ManW_TheUncool

    ManW_TheUncool Producer

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  7. JohnnyG

    JohnnyG Screenwriter

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    The on-screen horizontal resolution cannot be defined by the video amplifier bandwidth, but it IS a choking-point that can limit maximum res. For example, Toshiba's HDX series has a 30MHz video amplifier bandwidth, so the CRTs are getting every bit of an HDTV signal and then they do their best to display it. Panasonic claims a video amplifier bandwith of "greater than 10MHz.". You get about 80 lines of horizontal resolution per MHz of video amplifer bandwidth, so it takes 24Mhz to pass a 1920-line signal.

    It might seem simple to just open up the video amplifier and you'll get better on-screen resolution, but since the CRTs just can't resolve it, it might be better to limit what they get. It's all about designing a 'system' that works together.
     

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