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JP Compression artefacts - info?

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  • JP Compression artefacts - info?

    This has cropped up on the last few rejections I had and I wonder what the causes of this are?

    I know that there's nothing that can be done with the photos themselves, but how can I avoid it for future photos?

    I'm also wondering if using the same CF card over and over is a factor; I tend to do this, just wiping after I've uploaded them and then re-using the card.

    Are there any other things which can lead to this problem, which I can try and avoid. The odd thing is that this doesn't happen regularly, so I'm not sure what I do to cause it!

  • #2
    The easiest to avoid is:

    in camera:
    - shoot RAW
    - if you want to shoot JPG, save at the highest quality settings (some cameras also call it "JPG superfine", etc.)

    Post processing
    - Edit the photo and save the photo ONLY ONCE, AS THE VERY LAST STEP of your post processing.
    - Avoid noise recuders. I'm not 100% sure, but noise reducers cause fuzzy edges some times.

    You can use your CF card as much as you want, this doesn't have any impact at all.
    My photos on Flickr www.flickr.com/photos/geridominguez

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    • #3
      Compression is most often caused by....

      1. Saving as a .jpg several times during the course of processing.
      (Cure) Only save once, at the end of your processing.

      2. Saving at a low resolution.
      (Cure) Make sure that you save at the highest resolution. This is 12 in Photoshop. Also make sure that you set Baseline for the save.

      3. Setting the camera to a low shooting resolution.
      (Cure) Make sure that you are shooting at the highest resolution possible selectable in your camera. If possible, shoot in RAW format. Process the picture and make saving as a .jpg your very last action.

      I wouldn't think that constant use of a CF card would cause compression. Deleting data is a bit like washing a dinner plate. There's nothing left after you've done it !!
      If it 'ain't broken........ Don't try to mend it !

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      • #4
        Originally posted by brianw999 View Post

        2. Saving at a low resolution.
        (Cure) Make sure that you save at the highest resolution. This is 12 in Photoshop. Also make sure that you set Baseline for the save.

        !!
        This has happened to me a couple of times after setting up a new pc and reloading Photoshop.The default resolution is 10 I think so you need to increase this to the max(12 in Photoshop).
        A quick way to check if every thing is ok is after processing one of your latest photos is to bring the cursor over the thumbnail,then take note of the file size that is displayed and then do the same with the thumbnail of a photo on your pc that was previously accepted.There should be no great differance between the two.For example if one is 430kb and the other 480kb this should be ok as photos will vary some what.But if on the other hand one is 430kb and the other is 270kb then check what Brian outlined.

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