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Comment by planteen | Hacker News Reader

While the color depth of a JPG is 8-bits, it is not a linear 8 bits. The sRGB color space is gamma corrected (non-linear) and is roughly equivalent to taking the square root of a linear pixel value.

The same thing holds true for a processed RAW image as well.

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I'm going to be pedantic and air a pet-peeve of mine. "Raw" isn't an acronym. It's just shorthand for raw image data. It's not even the file extension of most (any?) camera raws. Why does everyone insist on writing it in capital letters?

Never really thought about that. I think I subconsciously interpret RAW as only meaning "file of unprocessed image data from a camera", whereas raw has more possible meanings. I know this shouldn't matter, because it's never confusing in context what one would mean.

I guess there's also the visual "symmetry" with JPG or JPEG.

Probably because it's cased that way in camera menus (correctness notwithstanding).

Another possible reason not outlined the other replies you received to this comment - If I were to say "copy the raw file" someone less experienced may think "okay, take the fresh jpeg file and copy it", interpreting "raw" in a more conventional, non-technical sense. Capitalizing it emphasizes that it refers to the file format, even if not the actual file extension. Sure, I could say "copy the NEF file" or "copy the CRW/CR2 file", but that means I'd have to know whether the user was using Nikon or Canon. "RAW" lets the speaker eliminate ambiguity in non-technical contexts without needing to be so specific as naming the actual extension.

Thanks for the reminder about JPGs, edited in!

When you say processed RAW, you mean after importing to image editing software, right? Which implies you wouldn't see much of a difference in posterisation in the high and low exposure areas

Right, after importing to image editing software.

Still, for a very long time the RAW file itself used to be linear in storing the signal. Perhaps not any more though.

It is still linear as far as I know. And the linearity is quite good, within a few percent. There is a community of astrophotographers interested in making photometric measurements with DSLRs (American Association of Variable Star Observers). I think the harder part of the problem is getting a standard candle for calibration of your DSLR DN values to actual SI quantities.

https://www.aavso.org/dslr-observing-manual

Huh, that sounds like a very interesting (but different) problem to tackle, given the vast differences between models.

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