[Openicc] L* was: MS on HDR CMS :)

[Jan-Peter Homann]

Hello list, hello chris,
Assumptions about the design of colormanagement workflows need always to 
be tested in practice. The idea behind L* workingspace and monitor 
calibration is to use the same lightness scaling as in the profile 
connection space L*a*b*

To analyze the differences from L* to Gamma 1,8 and 2,2 just do 
following tests:

1) Convert a scale with 256 steps of L*a*b* gray to RGB-workingspaces 
with Gamma of 1,8 and 2,2 and look about the resulting steps in RGB
2) Convert a scale with 256 steps of RGB Gamma 1,8 and 2,2 to L*a*b*and  
look about the resulting steps in L*a*b*

As the ICC colormanagement is based on L*a*b* as profile connection 
space, I think it is good strategy just to test if a L* RGB workingspace 
and monitor calibration has some advantages.

As a colormanagement consultant, I´m not a religious fighter for L*.
For users dealing mainly with sRGb and Adobe RGB images on monitors 
without hardware calibration, I recommend strongly AdobeRGB as main 
workingspace and monitor calibration with Gamma 2,2.

But I also think, that possible adavantages of L* workingspace and L* 
monitor-calibration should be tested in practice and also be analyzed 
with scientific research.

Regards
Jan-Peter

>> If we look at the standard gamma 1,8 and 2,2 we by converting equal 
>> RGB values to Lab, we see that the very dark RGB colors for Gamma 2,2 
>> don´t produce differences and for Gamma 1,8 we have it in the very 
>> light colors.
>
> What do you mean it doesn't produce differences? These workflows have 
> been around for a rather long time and rather well tested. They do 
> have reversibility so I don't understand what, in practice, is 
> actually being lost, if anything. Is this with respect to displayed 
> data and visual loss somewhere? Is this with respect to actual prints 
> and visual loss?
>
>


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