Quick develop and color space ...

Question

Ok, I know that library module previews are in Adobe RGB.
So, we view files which are in Adobe RGB.
But what about editing?
What color space we use when adjusting in quick develop in library module?

Answer 1

Armut12 wrote:
Thank you for such a clear summary.
Do you know why does Adobe not use Melissa RGB in library mode previews?
As far as I can see, assigning an Adobe RGB profile to a JPG file and assigning a ProPhoto RGB profile to a JPG file does not create any difference in file sizes.
Is there a disadvantage of using Melissa RGB in library views?
Melissa RGB isn't really a supported RGB working space. That is, it's not something you'll find anywhere outside of LR unlike say sRGB, Adobe RGB (1998), ProPhoto etc. It isn't installed or used by any other Adobe app. It's kind of a strange beast too: ProPhoto RGB with the sRGB gamma TRC. We'd have to ping the original LR architect (Mark Hamburg) to find out why he decided to use this odd space solely for RGB values and Histogram but I suspect the main reason is that viewing a linear encoded Histogram would confuse most users (it would look 'odd'). I can't say why he didn't just use the ProPhoto 1.8 TRC instead but that's water under the bridge. This space is not ProPhoto RGB due to the gamma encoding and it isn't used for processing! Only the RGB values and Histogram.
The actual color space used for processing has no name. It IS ProPhoto RGB primaries with a 1.0 TRC.
I suspect that using Melissa RGB or a similar huge gamut is unnecessary in any preview mode because:
1. Being so big, you'd want high bit (16-bit) data to reduce banding and that's overkill.
2. There isn't and never will be a display capable of previewing ProPhoto gamut.
3. There are a few displays that get close to Adobe RGB gamut, we may see that grow in the future. So might as well use that large gamut color space for previews. IOW, ProPhoto is way, way too big, sRGB is too small considering we have wide gamut displays.
IF you have Photoshop, you can build Melissa RGB and save that out as a profile. Only useful if you want to play around but has no practical use. In Photoshop's color settings, select ProPhoto RGB as your working space. In the same menu, now select "Custom RGB". The dialog shows you the "DNA" of ProPhoto RGB (white point, chromaticity values, gamma). Change the gamma to 2.2, save as an ICC profile. You now have Melissa RGB. You don't get the true sRGB TRC but a simplified one, but close enough.