Is raw a defined format? Or is it just whatever is most performant for the camera to write to storage, while also allowing for conversation to standard formats. Most are likely similar, running same or similar architectures, but in and of itself there is no raw format spec that must be adhered to. So if one way is more amenable to the system architecture, then that wins.

> Is raw a defined format?

It's not /dev/urandom written to disk, no. Yes, a raw format has a structure. There's not one "RAW" format though (and TFA notes this): e.g., my Canon's RAW format specifically referred to is called "CR3". And its predecessor was "CR2", so even within a manufacturer there are multiple such formats. All undocumented.

But a Pentax won't write out CR3s, it'll write out some other, yet bespoke format.

I've vaguely reverse engineered some of CR3: it is a container that contains multiple copies of the photo taken; IIRC it contains a thumbnail JPEG, the JPEG, and the raw data itself.

I doubt it's the most performant to write to storage: the format is vaguely TLV (its fairly similar to RIFF, if you understand the RIFF format), so it can't really be streamed to storage due to needing to know the lengths of the containing chunks (all the way out to the outermost chunk).