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Ilario5E19
Participant
April 18, 2021
해결됨

Does re-saving JPG changing DPI value (no re-samp) get worse the image quality? Re-compressing JPG?

  • April 18, 2021
  • 4 답변들
  • 669 조회

Hi everyone, newbie here.
I saved a JPG in Photoshop (quality 12 from an original PSD). It's 1200 DPI 5000x3000 px, without copyright infos saved.
Later I decide I want to add copyright infos but I haven't more the original PSD, so I open again my JPG in Photoshop, add the copyright, and save.
Later again, I decide I want to change the DPI value without resampling, so I re-open my JPG, set 266 DPI in Image Size maintaining 5000x3000 px, and save.

 

Question: since I re-saved my JPG twice, does it mean that I re-compressed my JPG twice as well? Does it mean the quality of the original JPG is now worsened?

Thanks in advance.

    이 주제는 답변이 닫혔습니다.
    최고의 답변: jane-e

    The JPEG format is lossy. It will degrade and lose information each time it is opened, edited, and saved again. The best practice is to keep the original, make the edits there, and export a jpeg once.

     

    ~ Jane

    4 답변

    Stephen Marsh
    Community Expert
    Stephen MarshCommunity Expert
    Community Expert
    April 18, 2021

    You can add/edit metadata such as copyright info without having to open/decompress the file using Adobe Bridge (scripts in Photoshop can also do the same).

     

    I am not aware of a way to change the resolution metadata in Adobe software without opening/decompressing. This is possible using 3rd party ExifTool software though.

      T
      Test Screen Name
      Legend
      April 18, 2021

      This is why keeping a PSD for every JPEG, every single one, is wise.

        jane-e
        Community Expert
        jane-eCommunity Expert답변
        Community Expert
        April 18, 2021

        The JPEG format is lossy. It will degrade and lose information each time it is opened, edited, and saved again. The best practice is to keep the original, make the edits there, and export a jpeg once.

         

        ~ Jane

          c.pfaffenbichler
          Community Expert
          c.pfaffenbichlerCommunity Expert
          Community Expert
          April 18, 2021

          »since I re-saved my JPG twice, does it mean that I re-compressed my JPG twice as well?«

          Yes.

           

          »Does it mean the quality of the original JPG is now worsened?«

          Yes. 

           

          You damaged your image unnecessarily. 

          Even in a case where file corruption or other data loss removed the original uncompressed image it seems imprudent to not keep an uncompressed version after the first editing of a jpg-damaged image. 

            jane-e
            Community Expert
            jane-eCommunity Expert
            Community Expert
            April 18, 2021

            Your reply wasn't there when I started typing, @c.pfaffenbichler, but appeared when I posted ! 😊

             

            ~ Jane

              c.pfaffenbichler
              Community Expert
              c.pfaffenbichlerCommunity Expert
              Community Expert
              April 18, 2021

              I think the same thing happened to me with one of your replies recently and with others’ replies, too, over time. 

              The important thing is: We did not offer conflicting information. 

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