Hi All!

Perhaps you could help track something down for me.

Years ago, I was watching one of those technology shows where they were discussing a new digital technique that could correct a fatally out-of-focus picture. Their argument was that all the picture "data" was still there, just in the wrong order. This new program would analyze the image, chew on it for awhile, and spit out a nice and crisp picture. They demonstrated it by framing in a shot of a billboard, and throwing the lens way out of focus before snapping the shot. The result was just a multi-colored blur. After digitizing it and running it through the computer, you could even read the fine print!

Has anyone heard of this? Does it exist? If so, is there a commercial package available, or is there a lab where you can send in ailing photos?

I'd appreciate any info you folks might have. No one seems to know the answer to this one. I swear to you I wasn't stoned at the time!

Thanks!

Sincerely, Wayne

-- Wayne Wilkinson (bobbachomp@earthlink.net), July 11, 2000

Answers

It's been possible for decades to retrieve some semblance of focus with blurred film images, by a technique known as spatial filtering. This can be applied to motion blur (camera shake) as well as out-of-focus blurring. However, the results always look like over sharpened digital images do, with diffraction rings around the detail. Not exactly what you'd call a "nice and crisp" picture.

The situation is slightly different with digital. Since a digital image can only store a finite amount of information, and usually much less than a film image, there's a limit to what can be done. I'd suggest that common or garden everyday techniques like interpolation and the ubiquitous "sharpen more" filter are approaching that limit anyway. Throwing more processing power at analysing a digital image is just looking for something that ain't there. You may be able to do things like making a slightly smeared image of a car number plate legible, but it will never look as good as if it wasn't blurred in the first place. I suggest the makers of the technology show were getting a bit carried away, and sensationalising some humdrum technique that was news to them, but old hat to the rest of the world. (How come science programs are always about 5 years behind the real cutting edge?)

-- Pete Andrews (p.l.andrews@bham.ac.uk), July 12, 2000.