From the GSMArena post:
We've traced the rise of the cameraphone before, but since we're in a lull in the megapixel race, we wanted to look back and check the milestones reached along the way to the Nokia 808 PureView - the 41MP monster that (five years later) is still the phone with the highest resolution camera (and only matched by Lumia 1020 since).
The Audiovox PM8920 may have been the first to cross the 1MP line with its 1.3MP camera in 2004. Niche brands aside, Motorola brought out the 1000 series phones that same year - the touch-focused A1000, the E1000 bar and V1000 flip. The Windows-powered MPx220 also joined in.
Motorola A1000 • Motorola E1000 • Motorola V1000 • Motorola MPx220
Then in early 2005 Samsung unveiled the P850, a flip phone with a rotating screen and a 3.15MP camera. Sound familiar? You may be thinking of the Nokia N90 from a few months later and its 2MP camera (with Carl Zeiss optics). Before the year's end, the Nokia N80 matched Samsung at 3.15MP.
And then looking ahead further in the article:
There was a brief flirtation with 13MP by Motorola and Toshiba, but Nokia put an end to the debate in 2012 with, yes, the Nokia 808 PureView - one of the best cameraphones of all time.
Its monstrous sensor was 1/1.2", the biggest we've seen on a mobile device. To put that in perspective, the sensor was 3 times the size of a 1/2.3" sensor like the ones we see in the Xperia XZ Premium, Google Pixel and a few others.
The sheer size of the sensor meant that despite its massive 41MP resolution, pixels were still quite large at 1.4µm (the Nokia N8 was at 1.75µm pixels). But the genius of the phone was elsewhere - mature image processing and leveraging on that resolution to enable high-quality digital zoom for 8MP photos. Advanced image processing is at the heart of the best cameras today.
Nokia kept things going for a bit longer, in 2013 it came out with the Lumia 1020 (running Windows Phone). It kept the 41MP resolution, though it shrunk the sensor to a still huge 1/1.5" (pixel size went down to 1.12µm). However, megapixel counts dropped off quickly after that.
The rise of resolution according to tech and then the fall again as other methods of achieving results came into prominence (e.g. what I've dubbed PureView take 2) is fascinating.
Also of interest might be my own 'Top 10 phone cameras of all time', in which I put the Nokia 808 at no. 4 and the Nokia Lumia 1020 at no. 5. Interestingly, my no. 1, the Lumia 950, isn't mentioned at all in the source article, probably because it focussed (pun intended) on fine tuning the innovations from the previous few years rather than breaking new ground in terms of resolution or pixel size.