RE: Lab -> RGB
RE: Lab -> RGB
- Subject: RE: Lab -> RGB
- From: Roger Breton via colorsync-users <email@hidden>
- Date: Wed, 6 May 2020 22:33:04 -0400
Wire,
We all know there is no such thing as an "absolute" AdobeRGB, as there is no
such thing as an absolute "P3" or absolute "sRGB" monitor, regardless of
brands or models or calibrations or profiling: put ten "AdobeRGB-calibrated
monitors" next to each other, they are bound not to show the same exact
colors, and we all know the reasons why, LCD vs LED vs IPS vs
instrumentation.... True, the better brands have reliable factory
calibration out of the box, which don't last forever, mind you. And even
then... And what about the rest? And who knows how a "creative professional"
might modify his/her monitor settings to "suit his/her taste"? I've seen
people change their settings behind my back... I think the case can be made
for whatever "RGB" space Jeff wants to use, it depends on his religion which
I'll respect.
/ Roger
-----Original Message-----
From: Wire ~ via colorsync-users <email@hidden>
Sent: Wednesday, May 6, 2020 9:40 PM
To: 'colorsync-users?lists.apple.com' List <email@hidden>
Subject: Re: Lab -> RGB
Reading your question carefully, you've asked for the widest gamut you can
get assuming a Lab source.
Have you evaluated how much of Lab your catalog actually requires?
Roger's (et al) point about value of sRGB assumption, even though somewhat
restrictive, carries the day in my view.
But I sense you already know and have a reason for why that's not
sufficient...
So what are your rendering assumptions?
I'll take a chance and offer a perspective on displays:
Given the commodities display market and the status of wide gamut today,
where new TV displays are reaching for but usually missing Rec.2020, that
would seem to be an appropriate max. For desktop computer displays, Display
P3 (Adobe Image P3) which is sRGB gamma is a practical compromise between a
significant additional (and balanced) extension to gamut with not-too-risky
backwards compatibility to sRGB w3c. It won't be outlandish if viewed wrong
but sRGB viewers will notice dull saturation. DCI-P3 is to be avoided due to
gamma 2.6.
Graceful handling of tonal response should be considered as important as
gamut, do that narrows the field quite a lot for backwards compat. You've
gotta think of both. Rec.2020 is nominally 2.4, pretty close but significant
variance from w3c sRGB
The safety of sRGB I consider very desirable. While it leaves some
real-world gamut on the table, no one is likely to miss it unless they know
exactly what to look for. An image in a wide-gamut space that is incorrectly
rendered due to lax ICC support is very likely to be noticed!
I don't intend to be purely contrary when I regard Adobe RGB as a one-off
space that can't be justified in any generally hygienic view of display
color. It was an error when it was created that was never corrected, and is
being forgotten with Display P3.
If you haven't reviewed Lindbloom chart, it helps get space performance re
Lab into a bit of perspective
http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html
The critical question I would consider:
Will your target be a display?
Or another app with subsequent processing?
If former, sRGB is safest
If latter, then pick the largest space that contains your catalog, but no
larger, and tend towards G2.2 TRC. ECI RGB v2 with L* TRC, a D50 whitepoint
and a wider gamut might make sense. It not likely to waste bits on color
that will never be used, minimizing noise injection.
FWIW
Yours
/wire
On Wed, May 6, 2020 at 5:00 PM Jeff Nova via colorsync-users <
email@hidden> wrote:
> Hi friends,
>
>
> We have a web application and want to display the best previews we can
> for Lab images, which are not supported by any browser. The Lab we
> expect is the default Lab from Photoshop, which I think is D50. So,
> what is the best choice for RGB space? We are tagging the files, and
> prefer v2 profiles for more browser compatibility, but will do v4 is
> needed. I don't need help in the transformation - I just want to know
> the best RGB space to present the widest gamut resembling Lab as possible.
>
>
> I assume one of the best choices is Don's MaxRGB?
>
>
> http://www.hutchcolor.com/profiles.html
>
>
> I welcome any input!
>
>
> Very best,
> Jeff
>
>
> --
> Jeff NovaChief Executive OfficerColorhythm
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