Question About Picture File Size...

Discussion in 'Digital Photography' started by Tknull, Aug 30, 2011.

  1. Tknull macrumors regular

    Joined:
    Jun 24, 2011
    Location:
    San Diego
    #1
    I could really use some advice about minor image modification. I'm on a mba using Lion. I occasionally make minor modifications to some photos (using Graphic Converter usually)... normally just minor cropping or editing out some small element of the photo I don't like. Nothing major. But I can't seem to save the image without the file size exploding.

    After making a minor change to the photo, I see three possible ways to proceed:

    1) Just Close the Image (Lion does not have the "save" option)... However, doing so I immediately see the file size go, in some cases, from around 100k to 900k. I can't fathom how a 900% increase in size is occurring.

    2) "Save a Version"... Not sure what is occurring here that is different than just closing the picture, as it is replacing/becoming the same file in the same location. Perhaps the only difference is that it is giving some settings options about the save.

    3) "Export"... Gives me a file type option, and settings.

    Options 2 and 3 seem to result in slightly smaller file sizes than option 1, but still 200% or 300% larger than the original. And this is with the settings showing 90% quality by default. So am i getting a lower quality image, with a larger file size...?
    Can someone please suggest the simplest way to save, with similar quality and file size, after a minor image adjustment?
    Thanks
     
  2. treestar macrumors 6502

    Joined:
    Feb 28, 2010
    #2
    You need to adjust the compression amount and/or file type. JPEGs are good for most everything but you need to mind the amount of compression and quality. I don't know anything about Graphic Converter but you can do all of those edits in Preview and possibly have better success.
     
  3. Tknull thread starter macrumors regular

    Joined:
    Jun 24, 2011
    Location:
    San Diego
    #3
    What I was trying to say is that a picture is already in a particular format, and set at some level of compression. I don't want to change that. If all I do, as an example, is edit out a smudge in a photo... and close out the photo, why would the file suddenly be several hundred percent larger. The compression level should not have changed. So why is the file suddenly so big?
     
  4. treestar macrumors 6502

    Joined:
    Feb 28, 2010
    #4
    I don't think there is any compression memory in image file types.
     
  5. admwright macrumors regular

    Joined:
    Sep 11, 2008
    Location:
    Scotland
    #5
    What happens is the program you have edited the file in does not know what compression level was used (afaik this is not stored in the jpeg file). When you open a file the program will 'create' all of the pixels needed to fully show the image. Your 100kb file goes to 6Mb say. Then when you save the file it will use it's compression algorithm (at it's current settings) to create the new version of the file. If this is different from the settings used when the file was originally created then this will result in a new file that is larger or smaller than what you started with. So if the 100kb file needed a jpeg level of 3 but your program is using a jpeg level of 8 the new file might be 900kb.
     
  6. snberk103 macrumors 603

    Joined:
    Oct 22, 2007
    Location:
    An Island in the Salish Sea
    #6
    You don't say explicitly, but it appears you may be using JPGs to save your images. Be aware that every time you save a JPG you lose some information from the image. Generally, the 1st JPG from your camera is the full file (or nearly so). The 1st time you save you lose some info. The 2nd time, you lose more. The 3rd time yet more again. It doesn't matter whether you make a big or small edit, because it's the act of compression that causes the data loss.
     

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