scott wrote:
>> No. Only if everything in the frame is at approximately the same focal 
>> distance does it approximate a 2D convolution.
> 
> I doubt that happens very often, usually the camera gets a point in 
> focus you didn't intend (and the bit you did intend is then out of focus).

No, as demonstrated, the problem I usually have is that my camera's 
optics physically can't focus near enough. That blurry image I posted is 
of a flat piece of ground. The focal depth is probably near-identical 
everywhere. (Except that I think the ground plane might be tilted 
relative to the camera...)

> But is it accurate enough to visibly improve the sharpness of an image? 
> Judging by all the software I've seen that claims to do this, usually not.

OK. That's kind of what I was asking. DSP theory says it can be done, 
but are the results worth it?

(DSP theory also says that a perfect deconvolution would require 
infinity gain at certain frequencies. You just *know* that's not going 
to work well in the Real World.)

>> This merely means that you can't deconvolve the edges properly.
> 
> True, more precisely a region half the size of the convolution kernel 
> along each edge.

For the image I'm thinking of, that wouldn't matter. The bit I want is 
the person's head in the center.

>> A much bigger problem is figuring out what the hell the convolution 
>> kernel might have been, given only the blurred image...
> 
> Indeed, and it might not be constant for every pixel.

I suppose if it changes sufficiently slowly, it might still be possible 
to estimate... maybe...

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