#186: Dusting for prints

I’m becoming increasingly frustrated by the quantities of dust I’ve been finding on all the optical kit to which I have access. Thinking about how best to remove or control the problem has led me to do some background research.

Then I started to think about whether this problem could be converted into some kind of benefit.

tom_hemeryk_dust417.jpg

In fact, if you have a pattern of dust particles on a glass screen protecting a sensor in a camera or scanner, then that pattern could be used as a ‘watermark’ to help defend your Copyright in the resulting images (assuming you were the kind of unrelaxed type who cares about that kind of stuff more than taking great pictures). This is today’s invention.

No one wants visible particles in their images, but it might be possible to take a calibration image of a very uniform field and thus establish the distribution of even invisible dust particles. This could then be actively sought, using statistical techniques, in all subsequent images taken.

The calibration image would need to be captured through the lens system and might be achieved by taking an image of the inside of the lens cover by briefly firing the flash, within the camera body, every time it is opened. This would probably require storing coordinates of the biggest 20 particles present and associating these values with the images taken in the current shoot.

If relying on natural dust ingress is an unattractive option, then I’d propose that every sensor array be manufactured with a unique distribution of minute biases (or that natural biases be recorded). These would be invisible when the images were viewed by a person, but could be detected by statistical image analysis techniques if Copyright, or tampering, were later at issue.

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