>>3524277Depends on the purpose, 99% of the time dynamic range and noise are more important than resolution.
>printsIf you want to make huge prints, you may need up to about 20 megapixels and a lense sharp enough to actualy make full use of your sensors resolution.
The lense more often than not is the limiting factor here, cheap kit lenses usualy aren't sharp enough for their sensors, a good prime stopped down on a full frame usualy is.
>UHD screensIf you have a 4K screen and want a picture with the exact same resolution you need roughly 8 megapixel to fill it, let's say 12 since the aspect ratio probably crops it a bit.
>Full-HD screensNow you're looking at about 2 megapixels.
>Instagram1.2-1.5 megapixels depending on the aspect ratio of your choice.
That's not even the full story, the larger the resolution of a sensor of a given size, the smaller the individual photosites get.
The smaller the photosites, the less sensitive they get.
Less sensitive photosites mean a worse signal/noise ratio, wich you see especialy at high ISO.
The lense also has to keep up in sharpness, wich especialy most zoom lenses can't do gor high resolution crop sensors.
That's why most high end bodies have about 20 megapixels on a large full frame sensor, as this gives them more than enogh resolution for anything short of billboard sized prints at high DPI, they use the full image of the lense instead of a crop for more sharpness and have insanely sensitive sensors.
(also billboards are usually low DPI prints as you only realy see them from far away)
TL;DR
No real point in having much more than about 20 megapixels, especialy when considering the trade-offs.
