Picture resize Always Too Dark...Help

Discussion in 'Digital Photography' started by Andrew, Nov 5, 2006.

  1. Andrew

    Andrew Guest

    Hello
    I am unsure if this is the group to pose this question to
    but i am starting to reach my wits end with this problem

    In a nutshell, I basically try to resize an Image from 640 X 480
    to 320 X 240
    the end result is a picture that is far darker and much less like the
    picture i originally started off with.

    I am presently using a batch resizing software called acdeesee 6.0

    I have tried using my canon powershot sd450
    then later have resorted to using an ATI capture card and my DV
    camcorder " Playback video of item" to capture stills
    the whole logic behind this is to capture hundreds of Pictures in a
    relatively short time frame " and in a perfect world, i might have
    little to no picture quality loss"

    Currently when i photograph a darker item " IE Shoes Etc"
    It appears brighter, then when RESIZED far darker?

    I remember quite awhile back, when i was still using Windows 98, I had
    a fixed setting of 320 X 240 on my capture card and it was absolutely
    amazing....Does anyone know why this can no longer be obtained with XP?

    I have purchased multiple camera's as well as 2 different ATI Capture
    cards to rectify this...Yet it still remains the same

    any info would be greatly Appeciated!

    Thank you kindly in advance for any responses
     
    Andrew, Nov 5, 2006
    #1
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  2. Andrew

    bruin70 Guest

    when you reduce the size of a pic, all the values get condensed into a
    smaller area and you've changed the spatial relationships. as an
    extreme example, take a look thumbnails of pics,,,everything becomes
    contrastier. there's probably some better explanation,,,like maybe a
    loss of value range in a smaller area,,,maybe a loss of middle tone or
    aomething.

    bottom line is you're eliminating 75% of the original.
     
    bruin70, Nov 6, 2006
    #2
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  3. Andrew

    bruin70 Guest

    or is it 50%....anyway, you get the point. you're losing a lot of
    picture.
     
    bruin70, Nov 6, 2006
    #3
  4. Andrew

    Steve Wolfe Guest

    In a nutshell, I basically try to resize an Image from 640 X 480
    When someone re-saves an image (or views it in a different application)
    and the colors are off, the answer is almost always that they're using a
    color space other than sRGB, and the application in question is not aware of
    color management - and hence, assumes that the image is sRGB, and munges it
    in the conversion.

    There are a few things in your scenario that lead me to think that *might*
    not be the case in your situation, but it's worth checking - what color
    space do you use for your photos, and if it's not sRGB (in which case, it
    would likely be Adobe RGB), is acdeesee able to handle that color space?

    steve
     
    Steve Wolfe, Nov 6, 2006
    #4
  5. Andrew

    Ron Hunter Guest

    If you think you can reduce the pixel count from 640x480 to 320x240 with
    'little or on loss of quality', I have a news flash for you: YOU CAN'T.
    If you reduce the pixels to 1/4 of the original number, you WILL lose
    the quality. You can't make a silk purse (or a cotton one) from a sow's
    ear. It can't be done!
     
    Ron Hunter, Nov 6, 2006
    #5
  6. His problem was about brightness, I thought?

    In any case, proper downsampling should not cause a significant loss of
    perceived sharpness or brightness level *for the new size displayed*.
    Yes, of course you lose some detail because of the reduction in pixels,
    but that doesn't seem to be the problem here. Given the quality of
    most video captures, you probably have nowhere near full 640x480
    quality anyway, so the reduction may actually help slightly!

    The colorspace suggestion was worth investigating, and another thing
    occurs to me - these are video captures, so do they perchance have
    interlacing, ie thin dark lines through them when viewed at full size?
    If so, the resampling method may be causing an issue. Try different
    resampling algorithms if ACDsee offers them, if not, download Irfanview
    and try that.

    If all else fails, post examples somewhere.
     
    mark.thomas.7, Nov 6, 2006
    #6
  7. Andrew

    Ron Hunter Guest

    If you think you can discard 75% of the picture data in ANY photograph
    and make it better, I don't care to see your pictures!
     
    Ron Hunter, Nov 7, 2006
    #7
  8. Gee thanks. (O:

    For low quality images like video captures, it depends entirely on what
    you mean by 'better'. Have you actually worked with such images, where
    the original may be interlaced with dark/repeated lines, or is motion
    blurred or out of focus? In those cases, downsampling and sharpening
    can provide a *smaller* image that does indeed look 'better'. And
    depending on the amount of blurring/interlacing, etc, there can indeed
    be no loss of detail.


    I routinely 'discard' much more than 75% image data to make my original
    images suitable for web-viewing, and as for the thumbnails... Just
    because I shoot a lot of my images as 18Mp RAW files, does not mean I
    use, need, or want all that data all the time. (O;

    And no, the reduced images are not 'better', but *for the size I wish
    to display them at*, they are as good as they can possibly be.
    Discarding picture data is only an issue if:

    1. It is real image *information*, rather than just data (eg interlaced
    lines or blurred pixels are *not* good information, just extra data).
    2. You actually need the data for the job at hand. (The OP clearly
    wants to reduce his images.)
    3. You don't keep the original! (only applicable if Item 1 does *not*
    apply) (O;
     
    mark.thomas.7, Nov 7, 2006
    #8
  9. Andrew

    Ron Hunter Guest

    You don't get better quality by discarding 75% of your data, period. I
    have worked with some low resolution pictures, and they get worse, not
    better when I try to do just about anything with them. Making them
    display smaller can appear to improve sharpness, but this is merely an
    optical effect as the blurry parts are skipped. If you call that
    'better', then a 1 pixel image would be the best. At least it wouldn't
    be blurry. Grin.
     
    Ron Hunter, Nov 7, 2006
    #9
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