Why Nokia went from 1/1.83 To 1/2.5?

[BilalSoomro17]

I saw Nokia N8 Camera and It have 1/1.83 Lens(Sorry if I am wrong) and why they have 1/2.5 on Nokia Lumia 1520? If they did 1/1.83 in 2010 why can't they do in 2014?

 

[DoctorSaline]

Err... It isn't lens. It is sensor size you are talking about. Nokia 808 used 1/1.3" and Lumia 1020 used 1/1.5" sensors. And 1520 used 1/2.3" and 930/icon used 1/2.5".
The reason is the larger the sensor, the more space it occupies in term of thickness. That's why 808 and 1020 both have camera bumps. 1/2.3" or 1/2.5" sensors can be accommodated while keeping the profile thin without the noticeable cost in quality. This also helps keep the price in check.