The whole question of lens sharpness...

Started Jun 12, 2013 | Discussions thread
GaryW
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Re: The whole question of lens sharpness...
In reply to Alphoid, Jun 22, 2013

Alphoid wrote:

olliess wrote:

Alphoid wrote:

In theory, given a perfect model of the lens, I can completely undo any blur caused by the lens.

I took this statement to mean just what it said, namely that you could undo any blur given a perfect knowledge about the blur function of the lens. To me, that means lens defects, diffraction, defocus, and anything else that modifies a point in the image.

My comment was, specifically, any blur caused by the lens. Diffraction, limited depth-of-field, antialiasing filter, resolution limits of the sensor, etc. are not caused by the lens. You would have those even with an ideal lens. Some of these are removable, and some are not. Chromatic aberration, spherical aberations, etc. are caused by the lens.

I had one photo in particular that was a bit unsharp due to diffraction -- not exactly blurry, but you could tell it wasn't sharp if you zoomed in-- and deconvolution completely rescued it.  It was like the blurriness was not even there.

I have less luck with countering poor focus, but for slight diffraction, it seems to work fine.

In addition, it's what DxO uses (I think) for their "lens sharpness", to counteract the effects of unsharp lenses, particularly in the corners where they use more intensity to counter the greater softness.  This seems to work to a large extent.

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Gary W.

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