Monday, April 26, 2010

The CMOS Rolling Shutter Problem

I will dedicate a more thorough posting to this issue some time soon, but much of the problem with the DSLRs out there today, as well as any small camera on a phone, flip camera or iPod, is the rolling shutter.

Check out this rainbow picture I took from my car, out the side window, while moving at highway speeds. Can you see the curve of the power lines? Doesn't it look a little unlikely?

It's unfortunate, but CMOS imagers are in use nowadays partly because they use far less power, which is a major consideration for mobile devices. I'll have to wait until we graduate to a better sensor technology than CMOS, that uses less power, or when battery technology advances adequately to the point that we can use less efficient sensors.

This rolling shutter artifact occurs because CMOS sensors read the image one line at a time over the course of the shutter time, and read from top left to bottom right, like a book, hence a rolling shutter, rolling across the image and line to line. You can deduce the orientation of the sensor, and therefore the camera if the image or camera are moving quicly. This is likely an interesting factoid in many forensics debates in courtrooms. You could determine which orientation and in which hand a camera was used because of this artifact!

1 comment:

  1. Nice blog for Home Security information,here I have got home security gates,Shutters,windows and grilles with the help of Rolling Shutter