Resolution question

Discussion in 'Blu-ray and UHD' started by JeremySt, Nov 28, 2008.

  1. JeremySt

    JeremySt Screenwriter

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    Ive always wondered this about bluray, but have never found the answer.

    On a standard dvd using Mpeg2, the horizontal resolution is 480. When watching a movie with an aspect ratio wider than 1.78:1, some of that resolution is used on black bars. So your resulting image is less resolution than 480, depending on exact aspect ratio. (2.20, 2.35, 2.40, 2.55, etc)

    Is the same true of bluray? Is a movie with an aspect ratio wider than 1.78:1 using some of its 1080 lines towards black bars?
     
  2. Reagan

    Reagan Supporting Actor

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    Hi Jeremy,

    The answer is yes. If the movie is of the 2.35:1 variety, then you have black bars eating up about 24% of the image, leaving about 820 lines free to display the picture.

    -R
     
  3. Joseph DeMartino

    Joseph DeMartino Lead Actor

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    Not quite. You're using "horizontal resolution" to mean "number of horizontal lines" - and that is incorrect. (Although you shouldn't feel bad, because almost everyone makes that mistake, inlcuding me.)

    The number of horizontal lines is actually the vertical resolution. And the exact number of visible lines under the NTSC standard is 482. (That's NTSC standard 525 less the 43 lines used to carry other data line closed captions.) Everything in NTSC has 482 lines - Mpeg movies, broadcast, VHS, laserdisc, all of it.

    Standard DVD does have a horizontal resolution of 480 - that is, 480 vertical lines of pixels measured from left to right across the screen. Widescreen sets have more rows of pixels because they are - well, wider. There are physically more phosphor dots or lquid crystal pixels or plasma cells on a widescreen set than there are on a 4:3 TV. That's why it is often said that while an anamorphic DVD will look better stretched out on a widescreen set because it is using more horizontal lines to paint the image, there is no actual increase in horizontal resolution. With Blu Ray, because the image can be encoded with more vertical rows of pixels, there actuall is more horizontal resolution.

    For a more detailed explanation, check out this article from 2001, specifically discussing horizontal resolution and SD DVD.

    Now, as to your actual question. (Remember that? [​IMG]) Of course. If your set has 720, 768 or 1080 horizontal scan lines and an aspect ratio of 1.77:1, and you're showing an image letterboxed to 2.35:1, some of those lines are inactive, just as in the old days of widecreen laserdisc, VHS and SD-DVD (letterboxed or anamorphic.)

    Regards,

    Joe
     

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