Episode 164: High Pass Sharpening

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Sharpening is a part of nearly every image processing. Selective sharpening allows to sharpen the important structures without to “enhance” the noise in the image. Already in Episode 6 I have shown a way to do this. And here is another way, High Pass Sharpening. It is often used in Photoshop tutorials and has no standard entry in the GIMP menus.

One step involves blurring – and this leads to a lot of different possibilities to change the effect. I explore asymmetric sharpening by blurring only into one direction.

Of course there are plugins available at the GIMP plugin registry.

A description of several sharpening methods is in our Wiki, I’ll add the high pass method today.

I got the recipe for this from a (very good) German book by Jürgen Wolf.

The TOC

01:48 Good German book: Jürgen Wolf, GIMP 2.6
02:00 GIMP 2.8 release late in 2011!
02:20 Preparing the image
02:40 Rotate
03:30 Crop
04:10 Contrast, black point and white point adjustment with the curves tool
05:30 The recipe for Highpass Sharpening
05:40 Duplicate the layer twice
05:50 Invert the colours
06:00 Set layer mode to Grain Merge
06:10 Blurring
07:00 Merge the top layer down and set the layer mode to Overlay
07:50 Adjusting the effect with the opacity of the sharpening layer
08:00 Sharpening in only one direction
09:50 What is Grain Merge doing?
11:00 How does this work?
14:50 Scripts at the http://registry.gimp.org

Creative Commons License
Meet the GIMP Video Podcast by Rolf Steinort and Philippe Demartin is licensed under a Creative Commons Attribution-Share Alike 3.0 Germany License.
Permissions beyond the scope of this license may be available at http://meetthegimp.org.

10 thoughts on “Episode 164: High Pass Sharpening

  1. Thanks for detailed set by step of what highpass sharpening is .
    you only can pick what type of sharpening when you know “what” its doing and what its sharpening in the pic .

  2. Hi Rolf,

    In watching your video podcasts over the last 2 years, you have inspired me to get more interested in GIMP and apply it to my digital art work and calligraphy. I have also learned a great deal from your podcasts. I want to thank you for creating and maintaining http://www.meetthegimp.org.

    I have just created my first GIMP video tutorial. It is about:
    -Using GIMP to do digital artwork and calligraphy
    -More on GIMP filters such as FIL1.6, Fx-Foundry, Gothic Glow, lomo, BW Film convert, color tint, etc…
    -and shows users how to use GIMP and Inkscape together for digital effects.

    Again thanks for inspiring me, and I look forward to more of your podcasts.

    My GIMP video tutorial is available at:
    http://steveczajka.posterous.com/the-amber-tutorial

    Let me know what you think.

    Cheers
    Steve

  3. This is a great way to sharpen especialy where theres areas of detail and where selective sharpening is being used. Its very similar to the frequency seperation approach your just adding another high frequency layer above the image.

    The way I have always done this is to duplicate my layer blur one copy untill the details I want to sharpen are just blurred. then setting the mode to grain extract merging the layer down, desaturating the layer stops any colour funkyness, and then setting the layer to grain merge.

    A great way to adjust the effect is what has been said already opacity, but another good approach is curves. As neautral gray has no effect on shapening setting a point in curves at 128/128 stops any changes to the mid gray point and then adding a sharp s curve really intensifies the effect with some crazy results.

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  5. Very interesting.

    Talking about unsharp mask, seems to me that the unsharp mask from gegl operation gives far better results (with perceived finer details) than the standard one from filters, using for example a 2-step 0.3-45 and after 0.5-0.5 as values.

  6. I need to raise raise the question in which point the USM process differs?! You also duplicate the background, blur it and find the difference. Does anyone have further information on this?

  7. Hey, really nice show, Rolf.
    I have always enjoyed when you decide to dissect some technique a bit and bring us there :-)

    Many thanks (again)

    Best

  8. I get a web page that display the following message instead of downloading the torrent-file, and an analogue page if I click the mp4-file.

    Not Found

    The requested URL /meetthegimp164.mp4.torrent was not found on this
    server.

    Apache Server at dl.meetthegimp.org Port 80

    • Retry it in some hours please, there seems to be again a problem with the server in Poland….. dl.meetthegimp.org should resolve to 94.23.46.181 then.

Anything to add from your side of the computer?