One reason is that photosites, like our eyes, are most receptive to light wavelights in the green range (500-600 namometers). Likewise, green light waves ae in between the red & blue positions in the light spectrum, and are found to some degree in most colors. Duplicating the green value gives the camera a better chance at discriminating between small differences in color and the amount of light (luminance) in a scene)...

Given three colours and the array pattern, it isn't possible to evenly group the photosites, so you have to choose either more colours (some Sony sensors), a different pattern (some new Kodak designs), or duplicate one of the existing colours. Green photon sensors are more sensitive than the other two, so they are duplicated. Although it would seem more logical to duplicate the least sensitive, gathering information about the luminosity is more important than gathering colour information..

Here is a link to a good intro to the techniques involved:http://www.liralab.it/teaching/SINA/papers/demosaicking-JEI-02.pdf.

Brian A...

To add to the confusion, in the world of painting the three primary colors are, red , blue and yellow.In photography it's red green and blue...........go figure!..

In printing the red and blue actually become magenta and cyan. The issue of primary colors of light, to which the eye is sensitive, and primary pigments of the art world, which work by subtracting light, and way way they work together to create the colors we see is one of the more difficult concepts I've encountered to get across to students in my 35 years of teaching physics...

In printing you're SUBTRACTING colours from those reflected. Cyan is all colors less red. Yellow is all colors less blue. Magenta is all colours less green.See http://en.wikipedia.org/wiki/CMYK_color_model.

Ledittmar wrote:.

To add to the confusion, in the world of painting the three primarycolors are, red , blue and yellow.In photography it's red green and blue...........go figure!..

That is the difference between pigments and colors. Pigments subtract the colors we don't want our eyes to detect. Red blue and green are the colors that actually enter our eyes, they are what our eyes actually detect. Simple concept, but largely misunderstood...

This graph* compares the sensitivity of the eye with CCD & CMOS sensors..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window.

Using twice the green filter area compared to red & blue areas on the sensor helps approximate the eye's high sensitivity to green..

Dave.

*http://www.fen-net.de/walter.preiss/e/slomoinf.html..

Thanks, this is quite informative. So I guess I can conclude that the main reasons are due to the limits on how you can organize the three pixel colors and that human eyes are most sensitive to the green color range. Sounds fair enough. Eli..