Colorimetry in EXIF

[Changed the subject in order not to hijack the main EXIF discussion]

On 2 January 2017 at 22:27, John Bowler wrote:
> That is correct, the camera information does not relate to the image in the
> JPEG (it might to the RAW image, but even that isn't certain).

I am by no means an EXIF expert, but from what I know, the colorimetry
is about the sensor. Once you have the JPEG, (or TIFF, or PNG) it
doesn't matter anymore. If you edit it further, that doesn't count,
either.

On one hand, if you modify the colorimetry parameters in EXIF (and the
raw processing software isn't smart enough to recognize what you
tampered with), the colors that get out of raw processing would be
off.

Conversely, you can alter the raw color processing, be it in camera or
in software (e.g. to natural colors, or vivid, or muted, or grayscale,
etc.); but the embedded EXIF colorimetry data would still be the same.

I haven't used any output color space except for sRGB, but even for
other gamuts (e.g. AdobeRGB), I assume that the embedded EXIF
colorimetry would still be the same.

One additional observation is about the distinction between the
colorimetry info stored in the EXIF chunk vs. the info in sRGB/iCCP.
The latter is about the output image and how to display it.

Sincerely,
Cosmin

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