Sensor Wars II - CCD vs. CMOS

An astute reader of this site pointed out that if CCD sensors generally produce better quality than CMOS sensors... and CMOS sensors are less expensive to produce... why is it that you find CCD's in so many lower-end digital cameras and CMOS sensors in so many "prosumer" digital SLR's?

Well, I don't pretend to know everything about digital cameras, but I think I have a pretty good idea of how this seeming contradiction works.

By most accounts, CCD sensors still generally produce somewhat better images than CMOS sensors. But there are a number of variables. One of those variables is pixel size. The smaller the pixels, the more likely your images will have noise.

Typical digital point-and-shoots have tiny image sensors. And the demand for higher resolution images has led manufacturers to cram more an more pixels onto these tiny chips. The result? More noise. The greater image quality available from a CCD makes it the obvious choice for these tiny sensors.

On the other hand, CMOS sensors are much faster than CCD's. They translate light into a digital signal right on the pixel itself. CCD's have to send a signal to the edge of the sensor before the translation occurs. When you have a full-frame (24 mm x 36 mm) sensor - one with realtively large pixels - the trade off in image quality isn't as great, and speed can take a front seat.

Cost may play a role here, too. The quality of a full-frame CMOS images is darn good - even if not as good as a full-frame CCD - but the cost to manufacture is so much lower, the CMOS makes economic sense.

The proof of the superiority of CCD image quality is clear when you look at products from high-end digital camera makers such as Hasselblad and Mamiya, where image quality is paramount. Their digital camera backs use CCD sensors.