Originally posted by traderdrew I just checked out the new Sony cameras in DxOmark.com. The 24 megapixel A77 and their other new camera do not score high in the low light category. It seems to be an impressive camera for outdoor use. Unless they come out with an improved sensor next year, it seems likely it will fall short of the low light capabilites of the K-5. I will just buy another K-5 when the price falls again.
The A77 loses 1/2 stop of light because of the mirror. That pretty much accounts for the difference in the DXO tests. Sony is also known to use a heavier color filter which gives it better color depth at the cost of higher ISO. I think we will see that the 24MP performs just as well as the 16MP in raw testing, and produces visually better looking images.
If the 16MP and 24MP sensor produce the exact same S/N ratio then the 24MP will look better and process out better. To use the term "pixel" loosely think of each pixel and film grain. The smaller the pixels the finer the grain. Noise will appear as a finer grain in the image.
Sony only provides the sensor. All the support architecture is supplied by Pentax or Nikon. The AA filter, RGB filter, IR filter, & image processor ALL play a big role in how clean the image looks.
Compare the Sony A55 to the K-5 and you will see a significant difference even though the use the same sensor. You can't judge how well the 24MP sensor will perform in a K-3 by using the A77 as a guide.