Skip navigation
Mr_Pedantic
Currently Being Moderated

Modified JPEG

Jan 1, 2013 5:02 AM

I just ran some file synchronisation software and it reported that a JPEG file had been changed on my C drive. I didn't remember changing it so checked. I have a trial version of Photoshop CS6. It seems that if a JPEG is opened into Camera RAW and then opened into Photoshop, then Windows reports it as modified, even if no changes were made.

 

My question is does this behaviour result in the image being resaved with a loss of quality each time that it is opened this way?

 
Replies
  • Currently Being Moderated
    Jan 1, 2013 5:59 AM   in reply to Mr_Pedantic

    Every single time any JPEG is saved (not just "opened") there's a loss of quality due to re-compression, no exceptions.  It doesn't matter whether you have modified it or not, nor does it matter whether the OS reports it as modified or not.

     

    Again, the compression occurs every time you save or resave a JPEG, any JPEG. Compression inexorably means image deterioration.

     

    The best solution is never to work on a JPEG, ever.  Use the format only as a final, target format when absolutely necessary but avoid it otherwise.

     
    |
    Mark as:
  • Currently Being Moderated
    Jan 1, 2013 6:05 AM   in reply to Mr_Pedantic

    It seems that if a JPEG is opened into Camera RAW and then opened into Photoshop, then Windows reports it as modified, even if no changes were made.

    Did you save or close the jpg without saving?

     
    |
    Mark as:
  • Currently Being Moderated
    Jan 1, 2013 6:16 AM   in reply to Mr_Pedantic

    Mr_Pedantic wrote:

     

    My question is does this behaviour result in the image being resaved with a loss of quality each time that it is opened this way?

     

    No. Camera Raw will write metadata into a JPEG without resaving and degrading the image. However, if you then save JPEG from Photoshop, that will result in degradation.

     
    |
    Mark as:
  • Currently Being Moderated
    Jan 1, 2013 6:33 AM   in reply to Mr_Pedantic

    Mr_Pedantic wrote:

     

    I closed the JPEG without saving. Windows still reports it as modified.

     

    Like I said, Camera Raw will have written metadata into the file without resaving and degrading the image. You can do a little experiment to prove that the image in the file won't be changed by Camera Raw. Hint: Photoshop can difference layers.

     
    |
    Mark as:
  • Currently Being Moderated
    Jan 1, 2013 6:28 AM   in reply to Mr_Pedantic

    Mr_Pedantic wrote:

     

    …Windows still reports it as modified.

     

     

    That doesn't matter.  If you just closed the file without saving, no compression or recompression took place.

     
    |
    Mark as:

More Like This

  • Retrieving data ...

Bookmarked By (0)

Answers + Points = Status

  • 10 points awarded for Correct Answers
  • 5 points awarded for Helpful Answers
  • 10,000+ points
  • 1,001-10,000 points
  • 501-1,000 points
  • 5-500 points