Couldn't we just change the resolution setting to 5mp then and in theory get a better quality photo?
That's really a quite excellent question.
The reason that I, as a single user example, take all my photos at 8MP is because that's what the sensor is going to see and do - 8MP.
Our phone doesn't provide this option - but just suppose and imagine that there were a 2MP mode. And let's imagine two identical photos, but made with that setting.
In such a case, you'd want some process to occur so that you're getting the sum of light across 4 pixels in 2MP, sacrificing some fine detail for greater light capture - you'd be integrating 4 pixels into one, in other words.
In theory, that's correct.
In practice, though, we don't have x-ray vision and so therefore cannot know what process really goes where inside our phone.
But - if you shoot everything at 8MP, you can improve your results by post-processing your snaps on your desktop. There, for example, you can resize your photos to a completely different dot pitch - and get that 4-1 integration - and you can post-process for all of the other wonderful subtleties such as exposure level and so forth.
I'm not saying that that process is perfect - I _am_ saying that I trust it a lot more on my laptop.
While none of the mobile phone processors are slouches in anyone's book - they just don't hold a candle to the graphics horsepower you can get on a desktop or laptop.
So, I take all 8MP from my phone - I even save myself some steps by preadjusting saturation, brightness, contrast, and sharpness - but those are just exposure parameters - I'm got the whole sensor image to play with.
If you go for 5MP, then your desktop processing options are limited.
Now, that said, here's the number one rule in photography:
There is no number one rule in photography. In fact, most rules - aren't.
So - I would highly encourage you to play with your camera settings, including the resolution. Maybe you don't want to be hassled all the time with desktop post-processing, for example.
Play with it. The only thing you care about in photography is the end result and answering this one question - are you happy? If the answer is yes, then you're all done, and to heck with the tech arguments.
Let me provide two examples.
This first one was taken as the sun was going down - no post-processing on the desktop, all adjusted on the phone. Note that the photo is grainy and the colors exhibit what we call banding, where the actual sensor range went to some low-bit-level in color.
And note how I don't care. I rather enjoy the limitations here - in fact, I've exploited them because enlarged, this has a other-world emotional feeling to it and that's more important to me as a reminder of that day than any National Geographic, eye-popping, precise photo could have ever provided me.
My second example is two little moviettes from a Fisher-Price toy camera - 2 colors, black and white - and bitrate, framerate, and frame size are laughable by our standards.
But note - creativity in photography is all about exploiting your camera, not giving in to it.
Made on a Fischer-Price toy camcorder - the PXL 2000 - from the '80s.
120 x 90 black and white pixels - 15 fps. Recorded video to an audiocassette.
They call it -
Pixelvision -
YouTube - Whitney (shot in Pixelvision) PXL 2000
YouTube - PXL 2000 Run
So - yes, it's darned important to get our video cameras working to the levels that Aldo is demonstrating.
But as I mentioned - once we hit a certain point, it's not about the megapixels, the lens or any of that - it's about you, the photographer, letting go of the hardware and capturing the moment.
Hope this clarifies, sorry if too long-winded and hope it didnt' come across as preachy, I was going for inspiring.