On 5D Mark III’s major technical features:

> … _what improvements has Canon made to the CMOS image sensor itself relative to the 5D Mark II?_

>> Three main areas of image quality-related improvement on the EOS 5D Mark III image sensor compared to the EOS 5D Mark II are:

>> · Gapless Microlenses: This feature increases the amount of light received by each photodiode compared to the gapped microlenses used on the 5D Mark II’s image sensor.

>> · New Photodiode Structure: The photoelectric conversion rate of each photodiode has been improved.

>> · On-Chip Noise Reduction: Canon’s proprietary technology in this area, which was first shown on the EOS D30 Digital SLR in the year 2000, has steadily improved over the years.

(via [CR](http://www.canonrumors.com/))