HTC’s 2013 flagship M7 will supposedly have a 4.3 Megapixel sensor instead of the rumored 13.1MP. HTC prfers calling it “ultrapixels” According to Pocketlint
The new camera will instead be made up of three 4.3-megapixel sensor layers combined to give a resulting single image.
The cameras in smartphones, compact point and shoots and DSLR’s mostly use Bayer sensor. Since 99% of all cameras are using Bayer sensor, this word is skipped in the specs sheet.
Each “pixel” in a Bayer sensor represents a red, green or blue photodiode and not all. These photodiodes are arranged in mosaic manner. An 8MP Bayer sensor will typically only 4 million green, 2 million red and 2 million blue pixels. The final image however has 8 million pixels where each pixel is a mix of Red, Green and Blue colors. This is achieved by a complex process known as “Bayer Interpolation”. Interpolation in simple language means introducing something between other elements or parts. Thus in Bayer sensor cameras the missing pixels are approximated to give final image.
A Foveon sensor uses 3 layers of sensors where each layer is made of pixels of single color. Thus an 8MP Foveon sensor typically has 8 million Red, 8 million green and 8 million blue pixels. There is no interpolation involved.
There are 3 times more pixels in Foveon sensors. This should give it a 3X advantage in resolution. However Bayer interpolation is more complex than simple re-sizing of the image. And Bayer sensors also use an anti-aliasing filter to gain sharpness. The output from an 8MP foveon sensor will have the same level of details as a 16MP Bayer sensor
If HTC is using the same technology, their 4.3MP sensor will have the same level of detail as 8-10MP image from smartphone cameras. Low Megapixel count should give them advantage in noise performance as the pixel sensor size will be larger than typical 13MP sensors. This also means better low light and high ISO performance.
It is also important to note that the technique is different from “oversampling” in Nokia 808 which has a 41MP Bayer sensor. Oversampling also eliminates Bayer interpolation hence 5MP Pureview images have better details than most 8-12MP smartphone cameras.