Debunking TV technology: Deblurring and enhancing photographs

This is one of my favourite debunks, largely because it is SO nonsensical: enhancing an image through deblurring, or image sharpening. As an example, I turn to Rizzoli & Isles episode “Tears of a Clown“. They are using a piece of video footage to once again find the location of a house. While searching through the video, one of the detectives says:

“Hey freeze it there”… “is that a window?”

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Followed by the other detective saying: “I can enhance the image”

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The original image is nothing but a blurry mess. Yes, there could be a window there, but considering it’s a house, and there is light coming in, it’s either a window, or a door. There is no way of recovering detail from such an image. To do that, you need more information than a small piece of video. Okay, sure it is possible to remove some forms of motion blur from an image. Blurring can  be described mathematically by the convolution of an image with an entity known as a point-spread function. So theoretically, blur can be removed if the point-spread function is known, however this deblurring is an ill-posed problem. It’s the result of optical blur caused by incorrect focus, or rather a shallow depth-of-field. Things close-up are in focus, those further away are blurred. We could try sharpening the image, but no algorithm would be able to recover the full detail – unless you tried matching against a slew of images taken from people’s basement (if such a database would exist, which of course it doesn’t).

Note also that the original blurred image only has dark information around the lower and right hand portions of the image. There is nothing that would indicate grilles in the window – so where did they come from?

Remember, Garbage in – Garbage out.

Here’s another case. In Numb3rs, episode “Pandora’s Box”, the team investigates a plane crash and the shooting of the forest ranger who discovered the crash. Charlie uses “wavelet deconvolution” algorithm to identify a smudged fingerprint, allowing them to identify the person who tampered with the plane’s software. It may be possible to remove some forms of blurring from a smudged fingerprint, if one assumes the blur is similar to the motion blur found in photographs. Blur of a more random nature may not be so easy to remove.

 

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