High pass (image processing)

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The high pass filter is a method for sharpening images. The filter looks for the edges in the image, i.e. places with large differences in brightness . The filter receives these edges in a radius that can be set in most programs , the rest of the image appears as a contourless, gray area.

Problems can arise if the process is overused. A luminous edge then forms around the highlighted contours. This also does not add any new information to the image, but merely improves the subjective impression of sharpness .

example

A picture that looks blurred due to a lack of contrast should serve as an example .

  • 1. Initial image (on which some geometric elementary corrections have already been carried out in advance) that looks flat and contourless

  • 2. High-pass display, radius: 5 pixels. The edge environment was obtained with a radius of 5 pixels, the rest of the image was reduced to a gray area

  • 3. End result by copying the high-pass display and the output image

literature

  • Klaus Kindermann: Photography for advanced users. Optimal use of photo, light and recording technology. Edited by Ulrich Dorn. Franzis, Poing 2008, ISBN 978-3-7723-6777-9 , pp. 276f.
  • Sibylle Mühlke: Adobe Photoshop CS5. The practical book for learning and looking up. Galileo Press, Bonn 2011, ISBN 978-3-8362-1586-2 , pp. 646f.