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erin km61901832
Known Participant
September 12, 2018
Answered

How do I maintain original file size?

  • September 12, 2018
  • 4 replies
  • 2679 views

Whenever I pull a file up in ACR or PS, make changes and save it, I asked to choose a size to save the file in. I dont want to resize the file. I want it to remain the same size it was when I got it. I have just been saving them at max, 12, but then I return files back to my clients much bigger than they were when I got them. This upset one of my clients a lot. So now I am in a position where I need to return some edited files back to this same client and every size I choose changes the original file size in some way. I dont want this. How do I maintain the original file size?

Thank you!

    This topic has been closed for replies.
    Correct answer D Fosse

    Jpeg compression doesn't touch resolution or image size, it's data compression to reduce storage and transfer footprint.

    The compression algorithm works by collecting blocks of pixels. It is much more effective on flat areas than on fine detail, so the more detail the image contains, the less effective the compression, and the larger the resulting file size.

    Now here's the important part: The compression introduces artifacts that for all practical purposes is added detail. This means that resaving a jpeg at the exact same quality setting will usually result in a larger file.

    Jpeg is a very special case among file formats. The compression is irreversible and cumulative. Resaving a jpeg is something that should be avoided if at all possible. You will never get the same file out as you put in, and there's no way to keep size constant.

    The only reason jpeg is still widely used, for all its problems, is that the compression is incredibly effective, much more effective than any other method. It can shrink a file down to 2-5% of original size, with no immediately noticeable degradation. But it builds up.

    4 replies

    D Fosse
    Community Expert
    D FosseCommunity ExpertCorrect answer
    Community Expert
    September 12, 2018

    Jpeg compression doesn't touch resolution or image size, it's data compression to reduce storage and transfer footprint.

    The compression algorithm works by collecting blocks of pixels. It is much more effective on flat areas than on fine detail, so the more detail the image contains, the less effective the compression, and the larger the resulting file size.

    Now here's the important part: The compression introduces artifacts that for all practical purposes is added detail. This means that resaving a jpeg at the exact same quality setting will usually result in a larger file.

    Jpeg is a very special case among file formats. The compression is irreversible and cumulative. Resaving a jpeg is something that should be avoided if at all possible. You will never get the same file out as you put in, and there's no way to keep size constant.

    The only reason jpeg is still widely used, for all its problems, is that the compression is incredibly effective, much more effective than any other method. It can shrink a file down to 2-5% of original size, with no immediately noticeable degradation. But it builds up.

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      erin km61901832Author
      Known Participant
      September 12, 2018

      Thank you!!! I learned in school how the compression works and was afraid the file size never being the same might have something to do with that. Thank you for explaining it so fully. I appreciate it. Now I can tell my client why the sizes are different.

      T
      Test Screen Name
      Legend
      September 12, 2018

      There is no magic to keep the exact size. Not in any app, it’s Impossible.

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        erin km61901832Author
        Known Participant
        September 12, 2018

        I was afraid of that. Thank you!

        Chuck Uebele
        Community Expert
        Chuck UebeleCommunity Expert
        Community Expert
        September 12, 2018

        I take it that you're getting jogs from you client. Removing them will cause degratuon, but I'm sure you know that. I would open them in PS first, and do a save as. When you do that, the compression used to save the original file should show up, it doesn't always, but you can use that as a guide. The other way would be to use save for web, it should show the saved file size, so you can get an idea of the compression to us.

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          erin km61901832Author
          Known Participant
          September 12, 2018

          Thank you! I can see the size of the file in the save as window and can tell its always different from what the size is for the same file in bridge before I hit the SAVE button.

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          erin km61901832Author
          Known Participant
          September 12, 2018

          To be clear, the dimensions remain the same, but the size in MB is always different.

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