This tutorial explains how Focus Magic photo deconvolution software can recover recorded detail from out-of-focus and motion-blurred images, and why low resolution and noise limit the result. Deconvolution models the way blur spreads each recorded point through the image and then works backward from that model.
The forensic ability of Focus Magic has been used by intelligence agencies, the military and law enforcement around the world. It has also been used in multiple court cases, including murder trials. For court cases, we have been asked to explain how Focus Magic works so that a jury can understand how the image was processed.
Detail can be recovered because each pixel becomes a circle which overlaps the other pixel circles.
The overlapping is done to a formula, so reversing the formula can recover a fair amount of detail.
For details to be recovered, the Blur Width needs to be at least 5 pixels.
Detail can be recovered because each pixel becomes a line which overlaps the other pixel lines. The overlapping is done to a formula, so reversing the formula can recover a fair amount of detail.
In this case, the After image is noisy because we set the Remove Noise setting to None in order to recover the most detail.
For details to be recovered, the Blur Distance needs to be at least 7 pixels.
Little to no detail can be recovered because the information is missing and there is no formula for recovering missing information.
For this licence plate, “RSJ 9594”, the characters are about ten pixels high, so we can recover a tiny amount of information. If the characters are only a few pixels high, no detail can be recovered.
For scanned photos, scan them using a resolution high enough to produce a Blur Width between 10 and 20. For example, if the photo was scanned at 1200 bpi and the Blur Width is 6, scan it again at 2400 bpi so that you can use a Blur Width of 12. If the image was scanned at the scanner's highest resolution, increase the image size as described for a digital camera below. Not all scanners produce sharp scans.
If you are scanning an image with quite a low Blur Width, it is vital to use a good scanner which does not contribute to the blur. After scanning the image, compare the real image with what you see on the screen and make sure the scanner has not added any blur. If you have the negative, you could make a large print before scanning it. Make sure the photo lab understands the importance of producing a sharp image.
If the photo is from a digital camera, increase the image size so that the Blur Width is in the 10 to 20 range. It is probably best to increase the image size by a factor of 2 or 4 so that the interpolation is kept as simple, and therefore as accurate, as possible.
If the Blur Width is greater than 20, scale the image down so that the Blur Width is in the 10 to 20 range. Focus Magic can process a maximum Blur Width of 20. Even if it could go above 20, there would be little or no additional gain.
A grainy image will not focus as well as a smooth, clean image.
Image with a normal amount of noise (grain).
Noise (10% uniform noise using Photoshop) was added to simulate a grainy image. The refocusing is not nearly as good.
If you already have an image, there may not be much you can do to remove noise or grain. If you have a negative, you may be able to reduce the noise by developing the print again using better equipment. If the image has dust on it, gently wipe the dust off.
For a video presentation of this tutorial, watch the Forensics video tutorial.