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Thread: Question about EXIF information

  1. #1
    Senior Member Ansel's Avatar
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    Default Question about EXIF information

    Hello,

    Reposting this question in this forum.

    Was looking at the exif info of my file and was wondering what some of the following info mean:

    X Resolution
    Y Resolution
    Resolution units
    yCbCr positioning
    Brightness value
    Components configuration
    Focal plane X resolution
    Focal plane Y resolution
    Focal plane resolution units

    Can anyone enlighten me? Thanks.

  2. #2

    Default

    I see you've posted again.

    I wanted to help you but seriously I have no idea too.

    But then I helped you do a search and come up with the following

    click here

    You can go download the files and read on your free time, I'm sure the answers are somewhere there.

    Hope it helps.

  3. #3

    Default

    Quote Originally Posted by Ansel
    Hello,

    Reposting this question in this forum.

    Was looking at the exif info of my file and was wondering what some of the following info mean:

    X Resolution
    Y Resolution
    Resolution units
    yCbCr positioning
    Brightness value
    Components configuration
    Focal plane X resolution
    Focal plane Y resolution
    Focal plane resolution units

    Can anyone enlighten me? Thanks.
    reading through, I managed to dig up a little information:

    XResolution
    Tag = 282 (11A.H)
    Type = RATIONAL
    The number of pixels per ResolutionUnit in the ImageWidth (typically, horizontal
    - see Orientation) direction.

    YResolution
    Tag = 283 (11B.H)
    Type = RATIONAL
    The number of pixels per ResolutionUnit in the ImageLength (typically, vertical)
    direction.

    ResolutionUnit
    Tag = 296 (128.H)
    Type = SHORT
    Values:
    1 = No absolute unit of measurement. Used for images that may have a non-square
    aspect ratio but no meaningful absolute dimensions.
    2 = Inch.
    3 = Centimeter.
    Default = 2 (inch).


    Ok, too lazy to cut and paste already.......

  4. #4
    Senior Member Ansel's Avatar
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    Default

    Quote Originally Posted by HelmetBox
    I see you've posted again.

    I wanted to help you but seriously I have no idea too.

    But then I helped you do a search and come up with the following

    click here

    You can go download the files and read on your free time, I'm sure the answers are somewhere there.

    Hope it helps.
    Yah, thanks HelmetBox! It is actually quite surprising most people don't know these!

    The site was really good, but a little too chim for me. Anywayz, thanks!

  5. #5
    Senior Member
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    Default

    Quote Originally Posted by Ansel
    X Resolution
    Y Resolution
    Resolution units
    yCbCr positioning
    Brightness value
    Components configuration
    Focal plane X resolution
    Focal plane Y resolution
    Focal plane resolution units
    i've always wondered myself, so i looked up the specs:

    XRes and YRes work hand in hand with Resolution Units. They refer to how 'dense' your pixels are supposed to be along both dimensions. For eg, if XRes is 72 and YRes is 72, and Res Units is inches, then your picture 72 pixel per inch in both the X and Y dimensions.

    YCbCr positioning refers to the way crominance and luminance information is positioned (relative to each other) in your picture - either centered or co-sited. See pg 25 of the exif 2.1 document in Helmetbox's link. (if you're really interested - there are some diagrams there.)

    Brightness Value: a number from -99 to 99 describing how bright the scene is. Exposure (Ev) is calculated from either

    Av+Tv (aperture and shutter speed)

    or

    Bv + Sv (brightness value and film sensitivity)

    Note that the Av and Tv here are NOT your f-numbers and shutter speeds, but converted to 'APEX numbers'. (If you really want to read the whole thing, it's page 152., Exif 2.1 PDF manual.)


    ComponentsConfiguration: when an image is compressed, it is either broken into YCbCr or RGB values. This tag describes which one are used and what order they are stored in. '1230' refer to YCbCr, '4560' refer to RGB.


    FocalPlane XRes/YRes/ResUnits: Same as XRes/YRes/ResUnits except that one refers to actual sensor resolution while the other is image resolution (i think). The quote from the spec is below - i can't really make sense of it:

    "These tags record the actual focal plane resolutions of the main image which is written as a file after processing instead of the pixel resolution of the image sensor in the camera. It should be noted carefully that the data from the image sensor is resampled. These tags are used at the same time as a FocalLength tag when the angle of field of the recorded image is to be calculated precisely."

  6. #6

    Default

    Nice one for the input

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