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LR ProPhotoRGB Gamma 1.8 and monitor calibration


Active Member
Oct 23, 2007
Perth, Australia

After learning that LR ProPhotoRGB is a Grey1.8 gamma working space, i wonder....

Does this have any relation/effect/consequense on how i calibrate my monitor?

Specifically, when i use my i1match 3, i set the gamma to 2.2. Should i be setting it to 1.8?

Or, am i on mars, and they totally unrelated?
Oct 7, 2007
Lightroom Experience
Power User
Lightroom Version
Where did you learn that? that doesn't sound right.

Use 2.2...

From a recent online conversation via email list:

Lightroom (and Camera Raw) uses a "working space" (meaning the processing
color space) of Pro Photo chomaticities (colors) and a linear gamma (1.'

Martin is correct to call LR's working space as linear, but (and this is
where it gets confusing), "Melissa RGB" (the color space coined by Mark
Hamburg) isn't the processing space of LR/CR but the display space in

Melissa RGB does indeed have the Pro Photo chomaticities but the gamma is
actually that of sRGB and the ONLY place where Melissa RGB is used is for
the Develop histogram and the color readouts.

There was a podcast with Mark Hamburg, Bruce Fraser, Zalman Stern and Thomas
Knoll where the whole "Melissa RGB" color space was discussed (I was there)
but because of the presence of alcohol (a Bourbon as I remember) the whole
thing got pretty confusing.

So, Lightroom's internal processing space is ProPhoto RGB in a linear gamma
(1.') but Melissa RGB is ProPhoto RGB with an sRGB tone curve. Also note
that the sRGB tone curve is not a simple gamma curve but is a tweaked curve
based on gamma 2.2 but with the toe adjusted.

And to answer the original question, no...you really REALLY don't want to go
down this rabbit hole at all. Just export out of Lightroom in the RGB space
you want to work in with Photoshop. Your choice is sRGB, Adobe RGB and
ProPhoto RGB.

Jeff Schewe