First photo is 48MP ProRaw; second is 12MP ProRaw

Both shot on the native camera app, nothing fancy turned on (not night mode, etc). I brought both into Lightroom (iOS), turned sharpening and noise reduction to 0, and bumped exposure +3.0 for emphasis.

Why does the 48MP photo look like it has been aggressively de-noised?

Curious if this is happening to anyone else. I downloaded a 48MP sample from one of 9to5Mac’s articles and it has the same problem, though the author doesn’t seem to have noticed.

Because it has been denoised. ProRAW is not RAW and there's still significant processing.

I've seen the same artifacts before but idk what exactly causes them.

If the problem happens to only you even when you download a sample from the internet then the problem is most likely on your side. Force quit, restart, try to update software. And if all else fails, Apple support. Good luck!

I’m sure the 12MP version also has some processing but it’s at least usable. The 48MP photo is just a blurry overprocessed blob.

I did some more searching online and have found others complaining about denoising in ProRaw but haven’t seen complaints specifically about 48MP ProRaw

The phone has an easier time processing the 12 MP version because it can combine the information of a four pixel square into one single pixel. But even then these tiny pixels can't gather enough photons to produce a clear image.

Something fancy like Night Mode would have helped here. Longer exposure means more light means lower ISO (sensor sensitivity) means less noise.

The iPhone will apply image processing (including noise reduction and its "Smart HDR" and "Deep Fusion" stuff) to the pure sensor data: About Apple ProRAW – obviously to a lesser extent and not as aggressively as for JPEGs.

But in edge cases like yours it's still a mess. That's why the middle of the speaker mesh is still visible. There was despite all the noise enough information to be worth keeping, while on the sides the mesh structure got so small that it was overwhelmed by noise and therefore reduced to… blobs.

Somewhere in this process the phone somehow does something that results in grid-like structures.

It's physics, followed by engineering. All we can do is to understand the principles and act accordingly. And maybe consider the Pro in ProRAW to mean "Processed" instead of "Professional" :D

I think that’s what I don’t understand about ProRaw… if the photo can’t be processed then why process it at all? I’d rather have a super noisy image that retains true sensor data than a “processed” image that loses all its detail.

What I’m trying to understand here is whether this is a bug (it must be, right?) or expected behavior. Unfortunately there’s no way of getting a regular RAW file out of the 48MP sensor, as far as I can tell

I don't think not processing is an option – after all, we are talking about Apple. If they deem something good (enough?) there is a chance it will become the default without any toggle.

I can't disable the "Smart" HDR function in my 13 mini. Only way around it is using the Lightroom camera (or any other third party camera app, I suppose). That also has the nice advantage of keeping noise reduction and sharpening to a minimum, which makes them my problem to consider afterwards. I also like noisy but sharp pictures better than the clean, oversharpened "smartly" optimized mess that has become normal.

Maybe try that? Lightroom saves DNG files (at least on my 13 mini, which doesn't offer RAW files otherwise). Maybe it gets the sensor data before any "smart" processing can take place.

As I said, your images are very difficult edge cases. I think even my mirrorless camera would have to ramp up the ISO to unuseable heights for this scene.

I used to use Halide for a while, and have tried Lightroom’s camera as well. Both are excellent for taking RAW photos. Unfortunately it seems like neither are capable of taking RAW 48MP photos, they’re both limited to 12MP. Maybe it’s an API thing that Apple skipped

From what I've read just now Halide should be able to – they offer "ProRAW" and "RAW", so there has to be a difference in… rawness :D

For Lightroom I just found complaints from September and October of last year and a standard "we're working on it". Don't know what's the situation now.

don't listen to bullshit mental gymnastics trying to explain why this is "normal". This is a bug, plain and simple. It shouldn't look like that no matter what. Try shooting with lightroom or any other app that has non-proraw RAW and see what it looks like, should be fine then