1 Reply Latest reply on Mar 26, 2011 1:23 PM by ssprengel

    NEF importing artefacts

    solarsd

      Hi,

       

      I have an issue when importing NEF images to Photoshop CS4. Apparently featureless backgrounds have strange, kind of "worm-like" structure on the single pixel level. Since these artifacts are a bit periodic in nature, sometimes they interfere also on a more sensible scale.

       

      The interesting part is that when I use UFRaw for importing, it seems that these artifacts are colour interpolation related. I've attached an image as an example (taken with a Nikon D40 + AF-S DX 35 mm / 1.8G lens: the top row contains samples of a white background, the bottom row samples a button feature. The first column is from Photoshop CS4, the second uses UFRaw's AHD colour interpolation, the third - UFRaw's VNG4C colour interpolation and the last column is again produced with Photoshop CS4 but a 1.0px sized Gaussian blur is applied since the images produced by UFRaw seem to be somewhat less resolved. Ignore the Moire patterns from the fabric.

       

      Sample.jpeg

       

      All settings were kept at their defaults, affecting the image as little as possible, except for the "Colour noise" reduction option in Photoshop, which was set to 25 by default. Lowering it produces similar result to UFRaw's AHD.

       

      Could someone would explain, where do these patterns come from and how to control them in Photoshop? Selecting a different colour interpolation algorithm in UFRaw helps, but I'd prefer to work with a single tool (Photoshop).

       

      Thanks in advance.