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Re: [OM] Spring Somewhere [was From our yard]

Subject: Re: [OM] Spring Somewhere [was From our yard]
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Fri, 22 Feb 2013 22:05:17 -0500
Thanks.  I now understand the cutoff.

Chuck Norcutt


On 2/21/2013 7:51 PM, usher99@xxxxxxx wrote:
> Dr. D writes
>
>>> No, you've got it.  I know diffraction is frequency related but I
> didn't
>>> understand the rest of what you said about sharp cutoffs.  You're now
>>> the leader.  :-)
>
> Point-spread deconvolution will not work all that well  to fix blur due
>   diffraction from a small aperture.
> Recall form the real Dr. D's link that on FT sensor by F11 max
> resolution is down to about 4MP overall and 3MP
> with red light.
>
> http://www.luminous-landscape.com/tutorials/resolution.shtml
>
>
> Unlike diffraction blur ,Gaussian blur "leaks" enough high frequency
> information into the image that it can be boosted and reconstructed
> (indeed, a gaussian is a very special extremum case that results in max
> blur for the least loss of high frequency detail)
>
> found the below images--not perfect but good enough
>
> original  image:
>
> http://praetoriusphoto.images.s3.amazonaws.com/fmforums/20120322_deconvolution/sinsweep.jpeg
>
> added diffraction:
> http://praetoriusphoto.images.s3.amazonaws.com/fmforums/20120322_deconvolution/diffracted_sweep.jpg
>
>
> note how detail frequencies above the cutoff are almost completely
> wiped out.
>
>
> Gassian blur added:
>
> http://praetoriusphoto.images.s3.amazonaws.com/fmforums/20120322_deconvolution/gaussian_sweep.jpg
>
> note gradual reduciton of high freq info rather than cut-off.
>
> Dr. Dp   (Diffraction protege)
> I trust Dr. D dosen't mind me keeping the training wheels on a while
> longer
>
-- 
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