He's right.
On digital cameras, ISO is just digital gain applied in the camera's post-processing (with the exception of dual-ISO/dual-gain sensors such as that of the GH5s and the BM Pocket 4K).
However, most cameras apply gain (and use different forms of noise reduction and image processing) before saving RAW. Only few cameras (like Blackmagic's) record ISO-invariant RAW files.
And ISO values between cameras are rarely comparable/rarely produce the same image brightness, as he points out.
Yeah - the cameras apply some processing before saving the raw file. In his side-by-side test with the Nikon, parts of the image looked a lot noisier (to me) in the one that he boosted in post.
The basic problem is that these camera influencers/reviewers lacks basic understanding of engineering it seems.
And ISO should have been called gain in still cameras also, like they use in video cameras forever.
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