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

[Chris Murphy]

On Feb 11, 2008, at 1:43 PM, Kai-Uwe Behrmann wrote:
>
> You emphasise printing only. But I'd think we see consuming of much  
> more
> media in form of movie, TV and so on or at least thise media are  
> growing
> compared to print. Print is no longer the only graphic output media.

I actually did not address this part previously, and being crazy I  
realize this three days after the fact.

The emphasis on print is not mine, but the ECI web site:

"The focus of the eciRGB_v2 profile still is on the print and  
publishing industry"

That's predominately an 8bpc workflow, and a TRC that's closer to  
gamma 1.8 function than L*. So I don't see the compatibility or  
usefulness of L* here.

The web site goes on to say it's recommend when converting from Raw  
data to 16bpc image data. Well if we have that many bits, it doesn't  
seem the TRC selection matters. The source data has no encoding, it  
may be linear, or close to it, and so when tone mapping all the way  
over to L* we have some loss. And then we have loss again as we tone  
map back to a TRC closer to print (or even display, movie or video).  
In practice the loss is greater for Raw because we first convert to  
gamma 1.8 or 2.2 space, then the workflow calls for conversion to L*,  
then back to some other TRC. It's a lot of conversions. If we were  
talking about medical imaging, with DICOM images and displays, then  
OK this is more compelling.

As you say other media are growing, but that's not mentioned for this  
color space. And the direction for most media is not improvement of  
8bpc workflows, but rather improvement for 16bpc and even higher bit- 
depth workflows where encoding is really pointless.

So I'm all ears if someone has a compelling explanation about L* and  
ECI-RGBv2.0.

Chris Murphy