Originally Posted by slipe
... The Z1 has a 22.6 sq/mm sensor and the 5700 has a 58.1mm sensor. So the pixels are considerably more tightly packed on the Z1. That generally would make the Z1 a noisier camera even though it has fewer Mp.
( Worth noting that the Nikon 5700 costs about twice as much as the Minolta Z1.)
I've not seen test data, but Slipe's comment makes a lot of sense. It seems that photo site density/size is a major determinate of noise, not pixel count. It will be interesting to see what the conclusions about the 8Mpixel cameras that are showing up with the same size CCDs (greater density and smaller photosites) as 4/5Mp cameras. Often with the same lens. Will they really be much of an improvement over the smaller/earlier versions?
Unless there is some other impovement (e.g., white balance, dynamic range, blooming, ...), I suspect there will not be even the 26.491.% increase in linear dimension that would be expected going from 5 to 8Mpixels in those cameras - noise will eat up much of the improvement that comes with increased pixel count. With any luck, that will slow down the "Mine Is Bigger Than YOURS" pixel count product developement and aim those resouces in other directions.