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  • JPG compression artefacts

    Had this rejected for 'JPG compression artefacts.' What am I to look for in the photo.

    http://www.jetphotos.net//viewreject_b.php?id=1768067

    Thanks, Barry

  • #2
    Just take a look at the sky, in the area above the aircraft there are the jpeg artefacts visible. They are the result of saving the image with low quality settings or multiple editing.

    I hope that helps you a little.

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    • #3
      Thanks degi. With this photo I think I equalized it twice to remove dust spots. That's where I got the artefacts.

      Barry

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      • #4
        I doubt, that equalizing a photo generates JPG compression artefacts. Usually you equalize a photo and undo this step, once you know where the dust spots are. JPG compression artefacts are caused by saving JPG file multiple times for example, or at too low quality settings, or even worse: a combination of both.
        My photos on Flickr www.flickr.com/photos/geridominguez

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        • #5
          Did you mean to say that you equalized and removed dust spots, then saved it, then went back and did it over?


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          • #6
            I think I equalized and removed dust spots, then saved it and equalized again to make sure I got all the dust spots. Had a photo rejected for CMOS dustspots and have been a bit paranoid about dust ever since, even after cleaning the sensor.

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            • #7
              Save the photo only when you've completed all editing and post processing. Everytime you save a JPEG you'll loose considerable quality. So ideally you should be looking to save only once before uploading.

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              • #8
                Hi Barry.

                I've also had a couple of rejections for "JPEG Comp.... artifacts" in the past and I have posted my doubts because I still can't know what they are. I'v posted my questions ( http://forums.jetphotos.net/showpost...&postcount=832) with no succes.

                I always used my camera with the highest settings when I shoot and I edit my pics and I save the file just when I finish the edition. Never before. But, I've had some rejections anyway for the famous jpeg artifacts.

                I'm still lost in this issue and someone told us above where he saw the artifacts but I have not seen any screener yet confirming that they where Degi said. In this pic I can't see them either. it'd very usefull someone could confirm if they are there or not.

                If I use the best quality and save following the general rule as I said before, I'm starting to think that they appear when the pic it's not good enaugh and you have to do too much edition or post processing.


                hope we could finally meet the artifacts

                Cheers,

                Fernando.
                _______________________________

                Will I ever repeat this?

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                • #9
                  Fernando,

                  After looking at my photo more closely, what I see as jpeg artefacts is what is refered to as 'orange peel' when paint is applied on a car. That's the best interpretation I can give.

                  I took the original photo and did the workflow over again. The photo was accepted. Did nothing different so I can't explain where the artefacts came from.

                  Barry

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                  • #10
                    Thanks for the feedback Barry.

                    best regards,

                    Fernando.
                    _______________________________

                    Will I ever repeat this?

                    Comment


                    • #11
                      Something to keep in mind is that a small amount of extra compression is applied upon upload here at JP, even if you upload a maximum quality image (100% from PS). It's barely noticeable most of the time but I have noticed it on blue sky backgrounds in particular.

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                      • #12
                        I got one rejected earlier for JPG artefacts, been reading through this thread and now know where I have been going wrong.

                        Cheers guys.

                        Ray.

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