scott wrote:
>> Echo, focal blur and motion blur are all instances of convolution.
> 
> Are you sure that focal blur is a pure 2D convolution?

No. Only if everything in the frame is at approximately the same focal 
distance does it approximate a 2D convolution.

> Ditto for motion blur - it's impossible to add motion blur by simply 
> using a convolution.

If the motion is "small" relative to the distance of the objects from 
the camera, then the blur should be approximately a 2D convolution.

>> That means, hypothetically, that by applying a suitable 
>> *deconvolution*, you should be able to get back the original signal.
>>
>> Question: Is it actually feasible to do this in the real world?
> 
> The problem is when you apply a convolution to an image, you get a 
> bigger image (the size of the original image + the size of the 
> convolution window). The extra data around the edges is needed in order 
> to do the deconvolution. Obviously in a photo you don't get this 
> information.

This merely means that you can't deconvolve the edges properly.

A much bigger problem is figuring out what the hell the convolution 
kernel might have been, given only the blurred image...

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