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Sharpening over-sampled images

 
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Beatsy



Joined: 05 Jul 2013
Posts: 1535
Location: Malvern, UK

PostPosted: Wed Oct 24, 2018 6:45 am    Post subject: Sharpening over-sampled images Reply with quote

For years I was of the opinion that pixel-level sharp was the only way to go. It didn't take long after joining this forum to be convinced otherwise! There is more detail (resolution) to be gleaned from over-sampled images at high mag (and N.A.). It's not *entirely* empty magnification.

However, the resultant fuzzy pictures continue to irk the "old me" a bit and I've tried many times to make them appear sharper. To date, nothing has worked to my satisfaction. Down-sampling does the trick, but restores sharpness and edge-contrast at the expense of (barely) resolved detail. Sharpening over-sampled imagery just causes halos and other artifacts that look nasty IMO. I tried adjusting radius and used many different sharpening protocols, and combos thereof, but never liked the outcome.

This issue mainly applies to microscope images of diatoms, taken using oil immersion to tease out close spaced punctae and other details at (and even beyond) the theoretical limits of resolution.

Am I missing a trick? Is it possible to improve edge-contrast and apparent sharpness of grossly or slightly over-sampled images without down-sampling them or introducing halos and false detail? Maybe there's a technique or two I haven't tried yet so any tips and tricks gratefully received. Thanks.
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Lou Jost



Joined: 04 Sep 2015
Posts: 3840
Location: Ecuador

PostPosted: Wed Oct 24, 2018 7:15 am    Post subject: Reply with quote

I know you don't like Photoshop but the RAW filter sharpening algorithm does not usually introduce conspicuous haloes (unlike the old Unsharp Mask).
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Pau
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Joined: 20 Jan 2010
Posts: 4859
Location: Valencia, Spain

PostPosted: Wed Oct 24, 2018 7:31 am    Post subject: Reply with quote

Maybe some deconvolution methods would do...although don't expect miracles

I've not yet tried this approach but I remember Rogelio Moreno results and discussions:

http://www.photomacrography.net/forum/viewtopic.php?p=134788
http://www.photomacrography.net/forum/viewtopic.php?t=21618
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TheLostVertex



Joined: 22 Sep 2011
Posts: 298
Location: Florida

PostPosted: Fri Oct 26, 2018 3:57 pm    Post subject: Reply with quote

Pau wrote:
Maybe some deconvolution methods would do...although don't expect miracles

I've not yet tried this approach but I remember Rogelio Moreno results and discussions:

http://www.photomacrography.net/forum/viewtopic.php?p=134788
http://www.photomacrography.net/forum/viewtopic.php?t=21618


Another thread for reference is https://www.photomacrography.net/forum/viewtopic.php?p=209154

Which might be more practical, since what is discussed does not have the same requirements as 3d deconvolution.
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