Question about PPI and battery life

[BlackZeppelin]

I've been reading about the OPPO Find 7 with it's quad HD display and the confirmed upcoming LG G3 that is also to have this. About 540PPI. On any article I read when I scroll down to the comments section, I always see some people lamenting about these ultra high PPI displays. Lamenting because they claim that high pixel display count means decreased battery life, for the same battery capacity as opposed to a lower PPI count.

I understand the logic behind this, as logically, more pixels means more power to light them. But is this actually true? I would have thought that regarding battery life and screen display, the only influencing factors are the type of display (AMOLED vs LCD) and actual screen size. If you have 2 phones exactly the same including size, but one has say 350 PPI and one has 550 PPI, it is still the same square cm area of display that has to be lit up, regardless of the size of those pixels in that display. If a pixel in phone A is twice the size of a pixel in a phone B and requires twice as much power per pixel, it still then only has to have half the amount of pixels to fill that display, compared to phone B. So cancelling the larger pixel size out. It doesn't matter, as I see it, if a screen is made of 1000 pixels or a 10,000,000 they still light up a finite screen size.

Appreciate if anyone could correct me.

 

[stkhalo07]

A fairly good article on this is: Do I Really Need a 1080p Display on My Smartphone?

Like you mentioned, though, screen size and type will have an effect. Higher PPI means more pixels/content for a screen to display, which in turn uses more GPU power and potentially CPU power as well. What's nice is that as the devices have gotten bigger, they've had room for bigger batteries, which help negate some of the differences seen from jumping from a 720p to 1080p screen, for instance (the article lists some examples). The performance tax on resolution is also apparent on the PC side as well, where dealing with content in 720 vs. 1080 - particularly gaming - (or even higher, like 1440p/1600p/4k) can require higher performing GPUs.