You can get a feel by how much post-processing is done by installing something like "opencamera" on a flagship phone, disable all filters and look at the raw file (if your phone allows it) and compare the results.
I went out with my android shitphone and someone brought their iphone 12 pro max. Here's a comparison (opencamera + rawtherapee vs iphone camera jpeg):
https://i.imgur.com/0E3KoBq.jpg
The iphone looks awful. It overbrightened/hdr-ed everything and made the sky blue (it was grey).
But, most people are happy with the default output from iPhone in most circumstances.
I have an iPhone and won’t likely switch to Android again any time soon, but it’s good to know that there are such flexible options now.
The Arri Alexa's Alev III sensor, which has won basically every Best Cinematography Oscar for the last decade, shoots at about 3k resolution (~7MP) yet holds up perfectly fine on huge cinema screens.
Majority benefit from shooting at a higher resolution is the ability to crop/zoom during processing. Sometimes, it's the ability to actually reduce the resolution to get rid of noise/grain.
I have an A3 print in front of me, from a photo taken with 24Mpx a7iii, and cropped a little in post. You’d never look at it and think “it needs more resolution”.
It’s not very hard to get moiré on a 45mpx sensor with a modern lens, hence we most definitely need higher resolution cameras. But even with a lower resolving power than that there’s an advantage.
Although I tend to just shoot on auto-exposure and bracket 3 shots, 0EV, -2EV, +2EV. One of those will usually give me what I want, without any messing around with dials.
FF cameras are great, but a totally different thing.
I took a XT-3 with me to Tokyo. While it’s a nice camera, I still found it too bulky but without the benefits of FF.
I ended up going with a A7R3 combined with a RX100. I leave the hotel room with the former gets taken when I know there’s something important I want to capture, if it’s at night, or when I know bulk isn’t an issue. The latter is taken when bulk is of concern.
FF = full frame, refers to sensor size. They are about 1.5x - 1.6x[0] in surface area compared to APS-C sensors.
Sensor size has various benefits in how you frame your photos, and can have larger sensor pixels at the same resolution, which can result in less noisy photos.
One such explainer of the differences: https://expertphotography.com/full-frame-vs-aps-c/
[0] EDIT: See below, this was a mistake; this is the crop factor, not the difference in surface area. It's more like 2.5x (depending on the exact camera/sensor.)
For example, you might using a FF camera with a 52mm f/1.2 lens, in order to get the very shallow depth of field this gives and/or the very high light-gathering ability. A good 52mm f/1.2 lens is expensive, but quite feasible (they've existed for many decades).
To get the equivalent effect with an APS-C camera, you would need a 35mm f/0.8 lens. As far as I know, no such lens exists (though it's theoretically possible to construct a lens as wide as f/0.5).
In practice, FF may have other advantages, due to engineering considerations. For example (though I don't really know), it might be that electronic noise from the rest of the camera has more effect on noise during pixel readout when the pixels are smaller.
Actually more like 2.3× in surface area.
Now I wonder, why would people buy FF cameras (especially if they don't shoot 35mm film cameras)? They are still bulky. Pick APSC or MFT which is smaller. If you want superb image quality without compromise, then skip FF and join the medium format club.
:D
Perhaps somebody is giving more priority to weight, size, price. Or lacks interest in shallow depth of field.
> Even if you love some APS-C lens, you can just mount it on a FF camera and crop.
Cropping a FF photo, especially from a cheap FF camera, may result in lower resolution than what an APS-C camera offers.
Anyway with used FF cameras now well under $1000, I have no idea why anybody would buy an APS-C camera. Even if you love some APS-C lens, you can just mount it on a FF camera and crop. Usually the camera will show you the cropped view in the viewfinder, but raw photos are taken at full resolution for you to manually crop later.