Lumia 1020 , smaller sensor ?

http://i.nokia.com/blob/view/-/2723846/data/1/-/Lumia1020-whitepaper.pdf

The white paper lists the sensor to be 1/1.5" , not the same as the huge 1/1.2" sensor in the 808. Slightly disappointed with this, but guess this had to be done to reduce the thickness.