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JPG compression artefacts

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  • JPG compression artefacts


    What are JPG compression artefacts, how can I recognize them and, last but not least, what can be done about it?

    See for example:

    Thanks for helping,

  • #2
    It happens when you save the image at a low quality or you have a low quality setting on your camera. The image does not display any compression at all. So sharpen it up a touch, take out the dust spot and re upload at the maximum allowable saving setting you can (photoshop is 12)


    • #3
      I too am struggling to see JPEG compression here, but in addition to the points already made there's one thing that hasn't yet been mentioned yet and that's the fact there's quite a strong blue colour cast on this image. This is caused by an incorrect white balance setting on the camera but is easily corrected in Photoshop (although it's much better to get it right when you actually take the shot rather than process your way around it afterwards). Here's the original:

      And the slightly edited version. The steps I made were:

      Slight Levels adjustment to give the contrast a bit more of a kick.

      Correction of the white balance using the Colour Balance tool in Photoshop. (Image-Adjustments-Colour Balance). For this particular shot I moved the Cyan/Red slider to +6 (towards red) and the Yellow/Blue slider to -6 (towards yellow). That was done on the default setting of Mid Tones and then the highlights as well (which can be selected at the bottom of the Colour Balance window).

      Add +20 saturation for a bit more punch.

      Add USM at 40%, Radius 0.3, Threshold 0.

      The result is:

      You'll get far better results re-editing the original and using the colour corrections I mentioned but there's nothing really wrong with that shot at all, it just needs a little work. One thing I do think is a slightly tighter crop would work better (I had to crop the copyright bar off to show this so I added another watermark, hope you don't mind!)

      Getting in that little bit closer gives a more focussed and dramatic image with more detail. Feel free to send me the original if you want me to edit it from scratch and I'll explain the exact steps I took in doing so. Just drop me a PM.

      Hope that helps.

      Seeing the world with a 3:2 aspect ratio...

      My images on Flickr


      • #4
        Brilliant tutorial, Paul! I'd combine the colors of #2 with the cropping in #3.
        My photos on Flickr