On Mon, Apr 11, 2011 at 12:36:58PM +0800, Sandy Harris wrote: > The usual sensor uses basically three types of element -- R, G and B > -- in a particular layout. > Why not X Y Z where X = R+G, Y = R+G+B, Z = G+B ? > > You can get RGB from XYZ easily enough: > > Y-X = R+G+B - R+G = B > Y-Z = R+G+B - B+G = R > > X+Z-Y = R+G + B+G - R+G+B = R > > But the total light you are accepting is 2+2+3 = 7 rather than > 1+1+1=3, so you are getting more photons overall. Isn't that > beneficial?
Not really. If all you are interested in is the total number of photons arriving at the sensor, you end up doing B&W photography. If you want the chroma components, though, you need to be able to approximate a measure of the stimuli that will excite the human eye. And, in particular, you want to be able to measure the individual R, G & B intensities, because that's how humans see colour. If you're measuring some linear compbination of the RGB components, you don't know whether a change in the measured value of R+G, say, is due to a change in G or to a change in R. The typical Bayer matrix - RGGB - is a good model for that purpose; it provides greater spatial resolution for G, because human vision is more sensitive at those wavelengths than it is at R or B. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
