> Echo, focal blur and motion blur are all instances of convolution.

Are you sure that focal blur is a pure 2D convolution?  If it was, wouldn't 
you be able to add physically correct focal-blur to a perfectly sharp image 
(eg a ray-traced image) with a simple convolution?

Ditto for motion blur - it's impossible to add motion blur by simply using a 
convolution (for example some detail might be hidden behind the moving 
object which then becomes visible in real motion blur).

> 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.

Post a reply to this message