Hello, IMHO the scanning artifacts are caused by the so-called rolling shutter effect. The issue is when each cell is "seeing" its individual shutter. When talking about a mechanical shutter it is almost the same time. Also valid for a so-called electronic snapshot shutter. It works global at each photosensitive cell at (almost) the same time. For instance high quality digital (CMOS or CCD) high-speed cameras need this type of shutter. Maybe you have a look at http://www.awaiba.com/en/technology/, especially the photos. (No, I'm not workig for them ;-) All can be more complicated when more than one read-out channel is present. With a cheap CMOS sensor you neither have a mechanical shutter nor a global operating one. Why? CMOS chip design would have a demand for additional transistors (in numbers: two) which would increase space and thereby costs. And CCD? Well, there are different designs. For instance (full) frame transfer CCD have read out times of some micro seconds and lower. But than they are costly. To get into philosophy: The universe is analog. (Digital doesn't exist. It's just a lie;-) It's obvious CCD gather light in an analog way. In simple terms like a solar cell. But so do CMOS. Even CMOS APS (active = amplification pixel sensor) count photons (or electrons) in an analog manner. What is done is one measures the current to re-charge the capacity at the pn junction of each cell. This value is amplified and digitally converted inside each cell electronics and then available as output on separate lines. Thus such a CMOS APS sensor looks to be digital when seen from outside. CCD, CMOS PPS (passive pixel sensors) which do amplification and especially A/D conversion outside the active area seem to be analog at first sight. Believe me, however, I can show you a CMOS APS which needs separate A/D conversion ICs even outside its housing. It's not suitable to say CCD is analog and CMOS is digital. Regards, Walter -- E-Mail: walter.preiss@xxxxxxxxxx HP: http://www.fen-net.de/walter.preiss/
