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Thread: Sharpening

  1. #1
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    Question Sharpening

    (I didn't find anything specific to my query, if this topic has been written about already please direct me to the post. Thank you.)

    Hello,
    Irfanview is a godsend application! It quite literally does everything we need for our project, we love it! And everything can be done within seconds using the batch feature.
    I recently considered sharpening images. The images we work with are scanned at 500 or 600 dpi; so upon testing the sharpening tool I notice that with some images it adds a "grainy" look. I'm unsure if there's any kind of option or alternative to bring a crisp look to an image without the "grain".
    Preferably would like this done in a batch because we work with hundreds of images at a time.
    Any feedback?

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    Multiple User jazzman's Avatar
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    Simple sharpening will bring out grain that is already there. What you need is a sharpning tool with a threshold parameter, so that only larger structures will be sharpened. There are photoshop filters (.8bf) out there* for that, but you wouldn't be able to run them in Irfanview batch mode.

    __________________________________________________ _______________________
    *e.g. Alois Zingl's sharpener here: http://members.chello.at/easyfilter/

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    I also have Photoshop. I wonder if it's possible to do it there through some kind of "batch" mode.

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    Multiple User jazzman's Avatar
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    I haven't got Photoshop, but yes I think it highly likely.

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    In Photoshop you perform batch conversion by first recording an "action" (on the actions palette) of all the processing steps including saving to a particular format, and then applying it to more images under File > Automate > Batch.

    For sharpening, try Unsharp Mask and adapt its radius to the size of the smallest features in the image (radius should increase with dpi). This will apply less boost to very high frequency single pixel noise than IrfanView sharpening, but will add more glow around edges.

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    Thanks j7n. I'll have to check that out.
    I just noticed there is an Unsharp Mask via Irfanview but I only see it in the image effects browser and it doesn't seem too bad. Just trying to get that minor blur out of scanned images. I'm assuming I can't batch such thing.

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    I don't see it in batch dialog either. The control in Irfan's USM isn't fine enough: only the first 2 or 3 levels are useful. There is only one parameter, where you normally need both radius and strength (I haven't found threshold useful, but it was suggested above). Photoshop CS2 is 'free' so it is easy to try.

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    RawTherapee, which is actually free and libre, offers very precise sharpening controls (unsharp mask or RL deconvolution) with a contrast mask preview.

    Click image for larger version. 

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    Plus a batch edit tool in the file browser. And so on.

    To get the latest, improved sharpening features, the development version is to be used. It is stable and safe to use.
    Last edited by Jacal; 23.10.2018 at 01:23 PM. Reason: Download link added.

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    Multiple User jazzman's Avatar
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    Quote Originally Posted by Doopz View Post
    Thanks j7n. I'll have to check that out.
    I just noticed there is an Unsharp Mask via Irfanview but I only see it in the image effects browser and it doesn't seem too bad. Just trying to get that minor blur out of scanned images. I'm assuming I can't batch such thing.
    It can be done in command-line mode

    From Irfanview Help:

    Code:
    Example for /effect=(effect-nr,param1,param2):
    
    i_view32.exe c:\test.jpg /effect=(6,3,0) 
    Apply Median filter, parameter = 3.
    
    i_view32.exe c:\test.jpg /effect=(2,3,50) 
    Apply Blur-2 filter, parameter1 = 3, parameter2 = 50.
    
    effect-nr values: (from Effect-Browser dialog): 
    1 = Blur
    2 = Gaussian Blur
    ...
    42 = Color Temperature
    80 = AltaLux
    I agree though that the effects are of very limited use. In fact, I never use them.

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