The whole question of lens sharpness...

Started Jun 12, 2013 | Discussions thread
olliess
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Re: The whole question of lens sharpness...
In reply to Alphoid, Jun 21, 2013

Alphoid wrote:

olliess wrote:

The law of entropy comes to mind.

There is no such thing as 'the law of entropy.' There is a quantity called entropy that is a property of a thermodynamic system. There are a few laws about it (you may be thinking of the second law of thermodynamics?),

Yes, I was referring to the second law of thermodynamics and its analogue in information theory. It's sort of like referring to Newton's first law as the law of inertia.

but it is difficult to see how they would apply.

Compare the heat/diffusion kernel to the (model) blur function of a lens.

There is no such thing as a 'diffusion-type process.' The blur of a lens is simply a convolution with the PSF of the lens. If the PSF is exactly known, it can be exactly inverted with a deconvolution.

First off, the problems of finite bandwidth, limited image extent, and noise will limit your ability to invert. And even you assume the PSF of the lens is known perfectly as a function of distance to the subject, it seems a stretch to assume that you know the distance to every point in the unblurred image.

Otherwise, it can be inverted to the degree it is known.

That's a far cry from a theoretically-guaranteed inversion.

http://en.wikipedia.org/wiki/Deconvolution

Thanks.

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