given file size limit, optimize jpeg level and resolution?

Discussion in 'Digital Photography' started by peter, May 24, 2006.

  1. peter

    peter Guest

    One of the classified ads site I use has a file size limit of 200KB on the
    photo and it has to be jpeg file.

    My camera is 6MP resolution and produces a 2MB file. Obviously I need to
    resize/recompress the file. But resize to what? I could keep the high
    resolution and use a high compression, or I could resize it to a low
    resolution and use a low compression. Which combination results in the best
    looking photo?

    I could use photoshop to resize the photo to different resolutions, then
    compress each one to just under 200KB, and then compare the end results. But
    this is too much work.

    Is there an easier way? I also have image ready, but I never use it. Would
    it help?
     
    peter, May 24, 2006
    #1
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  2. peter

    Bob Williams Guest

    If it going to be viewed on a computer screen, e.g. a web image, you
    should make the image about 600 x 800 pixels so it can be viewed without
    having to scroll around excessively. Save the image as a jpeg at Quality
    9-10 in Photoshop. Check the file size and adjust the compression
    accordingly if necessary.
    Bob Williams
     
    Bob Williams, May 24, 2006
    #2
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  3. peter

    Matt Ion Guest

    Yeah, what he said. Chances are the site is going to either re-shrink
    it, or constrain the display size anyway, so there's no point uploading
    a massive high-res, low-compression file anyway. 800x600 max JPEG with
    a medium-low compression (or medium-high quality, depending on the
    software used) should yield a file well under 100k, so size shouldn't be
    a problem.

    BTW, if all you're doing is resizing and resaving, Photoshop is serious
    overkill - with something like Irfanview (small, fast, and free) you
    could probably start the program, load the file, resize it, and resave
    it, in less time than it takes Photoshop to even start up. :)


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    Matt Ion, May 24, 2006
    #3
  4. Hi there,

    Try http://www.tangotools.com/jpegsizer/

    Hope this helps.

    Bye for now,

    George Dingwall

    Invergordon, Scotland

    http://freespace.virgin.net/george.gdingwall/index.html
     
    George Dingwall, May 24, 2006
    #4
  5. peter

    Jim Townsend Guest


    Ask them what pixel dimensions they want. (IE. 1600 pixels x 1200 pixels)

    Once you know this, then use Photoshop to resample your images to the
    desired dimensions. Reducing the number of pixels in each dimension
    will reduce the total number of pixels in the image. This will mean a
    a smaller file size when you save it.

    If the resulting file size is still too large, THEN add compression until
    it reaches the 200KB they want.
     
    Jim Townsend, May 24, 2006
    #5
  6. peter

    tomm42 Guest

    Agreed Irfanview is a great utlity for resizing, good algorithm etc.
    But it doesn't hold a candle to Photoshop for editing, enhancing, and
    sharpening files.

    Tom
     
    tomm42, May 24, 2006
    #6
  7. peter

    peter Guest

    I prefer as detail a photo as possible because when selling used items, it
    is advantageous to show the item without scratches, and 800 x 600 usually is
    not sufficient to show such details.

    When I am buying a used item, I also want to see a high resolution photo of
    the item. Having to scroll around is a non-issue when I have to make a
    buying decision based on the photo.
     
    peter, May 24, 2006
    #7
  8. peter

    peter Guest

    There is no restriction on the dimension. That is why I want to optimize the
    dimension + jpeg compression level.
     
    peter, May 24, 2006
    #8
  9. peter

    SteveB Guest

    It's not possible to give an exact answer due to the lossy nature of jpg
    compession. The more detail there is in the original photo, the harder it
    will be to reduce the filesize without introducing jpg artefacts.

    Paint Shop Pro 9 (and I think 8 and 10) has got a good jpg compression
    optimizer where you can see any build up in jpg artefacts in real time as
    you change the compression factor, this helps you squeeze the maximum
    compression before artefacts become visible. Typically, I wouldn't go
    bigger than 800x600 using a compression factor of about 7 to give 200k and
    very few artefacts. Any bigger (pixel dimensions) and it becomes really
    difficult with many photos to keep under 200k without seeing artefacts. You
    may get a slightly bigger image, perhaps 933x700 if you use some noise
    reduction first before applying extra compression, as artefacts may be
    fewer.
     
    SteveB, May 24, 2006
    #9
  10. peter

    Jürgen Eidt Guest

    cPicture can optimize picture size by given file size and quality when
    resizing.
    You can optimize any of the three by specifing the other two values.
     
    Jürgen Eidt, May 25, 2006
    #10
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