We all know that the megapixel race is pointless. However, the quality of a digital camera is all to often boiled down to 1 number, the megapixel count.
Unfortunatly there is much more to a good camera. Some are hard to quantify, such as optics, software, etc. Some lend themselves to check boxes, like optical image stabilization. Others such as sensor size and pixel size are easy to quantify, but lost, as everyone wants one simple number.
I was thinking about some type of scoring system that would rate sensors based on their total area, pixel size, and megapixels. Here is what I am thinking:
Effective (Eli's) MegaPixel Quality = Sensor Size in mm2 + ((pixels size in µm - 1) x MP count )
Nokia 808 = 101.4 EMQ
10.7 mm × 8 mm sensor size = 85.6mm2
1.38 µm pixels
Lumia 1020 = 63.1 EMQ
8.8 mm × 6.6 mm sensor size = 58.1 mm2
1.12 µm pixels
Sony Z2 = 31.8 EMQ
6.17 x 4.55mm = 28.1
Galaxy S5 = 28.6 EMQ
5.76 x 4.29mm = 24.7
Apple iPhone 5s = 21.9 EMQ
4.89mm x 3.67 mm = 17.9
1.5 µm pixels
HTC One M8 = 20.9 EMQ
5.44 x 3.07mm = 16.7
I tried to put the primary emphasis on the size of the sensor. I used pixels size in µm - 1, because the closer you get to 1µm, the closer you are to the wavelength of visible light and the more noise. Manufactures should be penilized in camera stats the smaller the pixels get. With this calculation they actually would start dropping in score as the size falls below 1µm, which is good.
I don't know that the units should be called or if this is the best calculation.