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Thread: Sharpening algorithms

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    Default Sharpening algorithms

    Hi,

    There are numerous ways to sharpen images, or selections of images, in NX, Photoshop, Elements etc. For overall sharpening a whole image, e.g. when downsizing, the simple viewers that are often free, e.g. Faststone for Windows and Preview for Mac, as well as ACDC and other quick and simple tools, all have a "sharpen" slider, which often seems to work very well. What algorithms do they use, and how do they compare to Unsharp Mask, and particularly to Smart Sharpen in Photoshop and Elements?

    Thanks,

    Richard

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    Richard,

    Check out the thread on sharpening:
    http://www.birdphotographers.net/for...read.php/18534

    Most algorithms I've seen in photography imaging processing programs are variants on unsharp mask, which as the above thread describes, do not actually sharpen; they just change edge contrast. Smart sharpen seems to be a variant of unsharp mask too, simply with different weighting on surrounding pixels. However, we can't be sure because the algorithms are rarely published in commercial software.

    True sharpening is an estimate and involves moving information from adjacent pixels. That is an iterative process that takes a lot of compute time, as in Richardson-Lucy deconvolution. There is no free lunch--you trade spatial detail for noise and if the blur model is not perfect, you get artifacts too.

    Roger

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    Roger,

    I've noticed you referring to the Richardson-Lucy deconvolution several times on these forums, I've googled it but can't find much info except relating to the heavy mathematical side.

    I am curious to know how you can use this "sharpening" method on bird photos as opposed to the regular "edge contrasting" algorithms of USM etc.. Is it available as a plug-in or incorporated in any commercial processing package like photoshop?

    Thanks,

    Nick

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    Nick,

    I'm aware of two image processing packages that have Richardson-Lucy algorithms.

    IRIS (free) http://astrosurf.com/buil/

    and ImagesPlus http://www.mlunsold.com/
    ImagesPlus may be coming out with a stripped down version of the software for photographers and it will include Richardson-Lucy. Not sure when it might happen but would be lower cost.

    Roger

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    Roger,

    Thanks for the info. The thread you referred to on sharpening was very instructive.

    Richard

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    Richard,
    Here is another article:

    http://www.clarkvision.com/articles/image-restoration1/

    Roger

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    Default

    Thanks for the links Roger, I'll give them a go and will be interested to see what results I get.

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    Try Topaz "In Focus" free trial. It uses a deconvolution method and/or edge sharpening technique.

    Works well on many images that are not tack out of camera.

    Chas

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    Thanks Chas. This could be the first deconvolution sharpening available in "for the rest of us" software. I already have the Topaz suite which I really like. I'll give it a try.

    I'm interested to hear what Roger thinks about it.

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    Robert Amoruso
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    I tried Topaz In Focus and it worked well though I have not decided to purchase it yet.

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    Chas, thanks for suggesting Topaz In Focus, I have downloaded the trial version. I appreciate each photo warrants individual tuning of the values but was wondering what sharpening values you find give good results overall for bird photos as I'm not sure where to begin setting each of the three sliders.

    Cheers, Nick

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