Originally posted by dosdan That used to be a problem in old designs. But with modern micro-lenses, the fill factor is quite large. FF can also be improved with a hexagonal sensel shape and staggered arrangement in the array. This has been done in the past.
Dan.
Right; The most modern design now is back illuminated sensor. You have a description here :
Back-illuminated sensor - Wikipedia, the free encyclopedia
Please note, that according to this source, 90 % of photons are gathered in this design. I don't think there is an application in APS-C sensor now, only for small sensors. Anyway with the presence of the bayer filters that select only one of the 3 primary colors, only 33 % of the light hit the detector.
And despite the fact that the light can be seen as a wave, Einstein has demonstrate that the power of the electromagnetic wave is transported by quantums of energy called photons. As I wrote, the best detector can only transform 1 photon into 1 electron, and this is the physical limit that will prevent performance improvement on high iso. Don't forget that moore law applies to microprocessors, not sensor. And even on microprocessors, when transistors will be so small that the will deal with a very limited number of electrons, moore law will not be applicable anymore.