I actually asked Sony Support about that. Their reply: "We can confirm that with Lossless compressed RAW there is a minimal quality loss. To have no impact on image quality I suggest using Uncompressed RAW files." Lossless isn't what it used to be.

Seems you just got 1st line robo-reply repeating what public resources state. Does not say much about actual compression algorithm Sony uses.

Their first reply was "we have passed your question to a higher technical team", then they came back four days later with the above reply. I was enquiring about the A7R mark V, which introduced the much needed "lossless" option. I think I asked because I wondered why they kept the uncompressed option and because experts warned that Sony did that before with "lossless" formats.

It is a shame that Sony has such an obsession with weird proprietary formats.

They read it lessloss I guess

That's insane. I honestly thought that lossless basically means to run zip over the file and not more.

Gotta hate companies these days with their dishonesty. "Lossless" means "lossy". "Unlimited" means "limited to 50GB".

A lot of cameras write "lossless" to mean "perceptually lossless". This is easy to do because ~12-bit ADCs have lots of noise in the low order bits.

"lossless" has always referred to compression, not sampling - but it seems camera manufacturers want to change that for marketing reasons.

Similarly (without starting an audiophile thread): Recording a vinyl record and compressing to a MP3 is "perceptually lossless" but will be different to compressing to a FLAC, never mind that the sampling output will always have random noise.