cropping for hdtv

Discussion in 'Digital Photography' started by mark_digital©, Oct 20, 2003.

  1. How do you treat an image so it will fill a wide screen HDTV without
    vertical or horizontal bars? Is it as simple as cropping an image to 16:9
    ratio?
    The 480, 720 and 1080 are confusing. Do these selections have to be
    considered when getting still images ready for HDTV?
    Thanks, and you'll save me many trips to the electronics store.
    Mark_
     
    mark_digital©, Oct 20, 2003
    #1
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  2. mark_digital©

    Savidge4 Guest

    >How do you treat an image so it will fill a wide screen HDTV without
    >vertical or horizontal bars? Is it as simple as cropping an image to 16:9
    >ratio?
    >The 480, 720 and 1080 are confusing. Do these selections have to be
    >considered when getting still images ready for HDTV?
    >Thanks, and you'll save me many trips to the electronics store.
    >Mark_
    >


    Mark,

    I have found that if you acuratly match your photo resolution with your TV
    resolution you will get the results *YOU* want and not the results of a
    conversion. for standard TV I create photos that are 720x480 at 200 DPI and
    get great results.

    And before the DPI bashers slam on me... try it before you open your mouth.
    there is a difference between a 72dpi image and a 200dpi image when viewing on
    a TV.

    Anyways your answers will be in your Manual, so you can determine the exact
    resolution for your TV.

    Hope that helps!
     
    Savidge4, Oct 20, 2003
    #2
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  3. mark_digital©

    Mark Spatny Guest

    mark_digital©, says...
    > The 480, 720 and 1080 are confusing. Do these selections have to be
    > considered when getting still images ready for HDTV?


    For 1080i HD, which is the most commonly used HD format, it is not
    enough to have your images in the 16x9 aspect ratio. Your pictures
    should be 1920 x 1080 pixels. And forget what the other gentleman said
    about screen resolution. When your image is transferred to tape or
    loaded into a computer for visual effects work, the only thing that
    matters is the pixel dimensions. DPI doesn't enter into the equation,
    since no video tape machine will ever see that setting. 72 DPI or 200,
    makes no difference.
     
    Mark Spatny, Oct 20, 2003
    #3
  4. mark_digital©

    Samuel Paik Guest

    "mark_digital©" <> wrote in message news:<bmvgmi$aju$>...
    > How do you treat an image so it will fill a wide screen HDTV without
    > vertical or horizontal bars? Is it as simple as cropping an image to 16:9
    > ratio?


    Roughtly speaking, yes.

    > The 480, 720 and 1080 are confusing.


    In what way?

    > Do these selections have to be
    > considered when getting still images ready for HDTV?


    Possibly.

    The ATSC DigitalTV/HDTV recommendation has these resolutions
    for widescreen:

    1920x1080 (square pixel)
    1280x720 (square pixel)
    704x480 (NOT square pixel)

    At this time, local digital broadcasts in this area (just south
    of Washington DC) include:

    WRC (NBC): 1920x1080
    WTTG (FOX): 704x480
    WJLA (ABC): 1280x720
    WUSA (CBS): 1920x1080
    WETA (three subchannels) (PBS): 704x480 (all three)
     
    Samuel Paik, Oct 20, 2003
    #4
  5. (Savidge4) writes:

    >I have found that if you acuratly match your photo resolution with your TV
    >resolution you will get the results *YOU* want and not the results of a
    >conversion. for standard TV I create photos that are 720x480 at 200 DPI and
    >get great results.


    That won't necessarily work; it depends on your frame buffer (graphics
    card) and software.

    Ordinary TV sets are 4:3 aspect ratio. An image that will just fit the
    screen while using square pixels (the usual default in digital
    photography) is 640x480 for NTSC (larger for PAL).

    Now, digital video hardware normally uses non-square pixels, and 720x480
    is standard for an NTSC image. If you want to put a digicam image in
    this format, you'll have to *first* crop it to 4:3 (either 640x480 or
    720x540) to get the right shape, then resize it to 720x480 to get the
    proper aspect ratio non-square pixels. Then you have to load it into
    a frame buffer that will actually display the non-square pixels
    properly.

    If you just crop a digicam image to 720x480, you have a 3:2 aspect ratio
    image being displayed on a 4:3 aspect ratio screen, and the image will
    be "squeezed" horizontally.

    Conversely, if you acquire a digital video image that is 720x480, you
    need to resize it to either 640x480 or 720x540 to make things appear
    the right shape on a computer. If you don't believe me, just shoot
    something that is round with a digicam and a video camera, import the
    images, and display on computer monitor or TV. If a round object turns
    elliptical, your image is distorted.

    Normally, computer frame buffers and monitors are set up for square
    pixels, and graphics cards with NTSC output (unless they are specialist
    items intended for video editing) also display square pixels. So the
    displayed size is 640x480 or something close to that.

    Dave
     
    Dave Martindale, Oct 21, 2003
    #5
  6. mark_digital©

    Mark Spatny Guest

    Samuel Paik, says...

    > WTTG (FOX): 704x480
    > WETA (three subchannels) (PBS): 704x480 (all three)


    Keep in mind that although digital, these are *NOT* HDTV. Not all ATSC
    signals are considered High Definition.

    > WJLA (ABC): 1280x720


    Even shows that broadcast 720p on ABC (Threat Matrix, for example) do
    their post production at 1920 x 1080. The network downconverts for
    broadcast. I work in a post production facility that handles about 20
    network TV shows, most of them in HD. I spend my day managing artists
    creating graphics for those shows. For HD, we use 1920 x 1080
    exclusively. If you want to size your photos at one resolution, that's
    your best and safest bet.
     
    Mark Spatny, Oct 21, 2003
    #6
  7. mark_digital©

    Jim Townsend Guest

    Savidge4 wrote:


    That makes sense.. I guess all you have to do is resize your image so the wide
    end is 720, then crop it at 480... Presto, a 720x480 image.

    Have you tried going double the size (1440x960) ? Seems that might provide a
    bit more detail.

    > And before the DPI bashers slam on me... try it before you open your mouth.
    > there is a difference between a 72dpi image and a 200dpi image when viewing
    > on a TV.


    Well.. The only thing you're changing when you change dpi is a couple of bytes
    in the header of the file.. -No- other data in the image file changes. But
    if you see a difference, good for you :)
     
    Jim Townsend, Oct 23, 2003
    #7
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