6 Replies Latest reply on Jun 26, 2016 6:08 AM by trshaner

    Highlights and Shadows Artifact

    kdiefendorff Level 1

      I have been noticing in many of my Lightroom-processed images a strange double-edge artifact at various places in the images.

       

      In looking into it, I have isolated the problem to the Highlights and Shadows sliders. Specifically, on soft edges between bright and dark areas with the Highlights slider moved to negative values and/or the Shadows slider moved to positive values.

       

      You can easily see the problem by creating a simple file (in Photoshop) with a black square on a white background and applying a small Gaussian Blur to soften the edge. Then open the file in Lightroom and move the Highlights slider left to -100 and/or the Shadows slider right to +100.

       

      What you will see is very noticeable banding around the square. But this is not just some theoretical thing you can see on a contrived image. It happens and is very noticeable in real-world photographs. While the double-edge is sometimes not visible with the image zoomed out, the double-edge creates an apparent softness in the edge that actually makes it appear softer than the original edge. But when you zoom in on the edge you can see that it is not softness, it is actually a double-edge distortion.

       

      I have verified that the problem also exists with the Highlights and Shadows sliders in the Photoshop Adobe Camera Raw module. So the problem is really with the Adobe Camera Raw processor, not Lightroom itself. The problem does NOT occur with Photoshop's internal Shadows/Highlights Adjustment module.

       

      My guess is that Adobe Camera Raw is using an inappropriate window function for selecting the pixels it darkens or lightens.

       

      Anyway, this is a big problem for me. The Highlights and Shadows sliders are essential features for photo processing in Lightroom. The double-edge artifact created by appreciable negative Highlight values and/or appreciable positive Shadows values is strongly accentuated by moderate amounts of sharpening by Lightroom's Detail module. This artifact is so strong that it limits Highlights and Shadows adjustments to a range narrower than necessary for many photos.

       

      Has anyone else noticed this problem? Anyone know of a workaround (other than avoiding the Highlights and Shadows sliders, or using them only by tiny amounts)? Does Adobe know about the problem and have a plan to fix it?

       

      --

      Keith