Re: [Openexr-devel] Colour space

[Chris Cox]

Yet neither RIMM nor ERIMM are linear (gamma 1.0) colorspaces. 
OpenEXR files are supposed to be gamma 1.0.    So  you can't apply 
those colorspaces as-is.


> The problem with RIMM and ROMM, as well as with XYZ and most other 
> systems (e.g. Rec 709 HDTV) is
>  that the color primaries are specified in terms of CIE 1931 xy 
> chromaticity coordinates.  This is also true for
>  the primaries in the OpenExr header.

That's not a problem - that's the standard, with good reason.


> CIE 1931 xy chromaticity relies upon x_bar, y_bar, and z_bar 
> spectral matching functions, which are known to
>  have some errors in certain color regions (especially near cyan at 
> 500nm, but also at other places in the spectrum).

Not much error according to the reasearch I've seen.
Yes, it could better account for women with a fourth primary sensor 
and color deficient viewers.


>  I have been inquiring of color scientists concerning a) how much of 
> a problem are the errors in CIE 1931 XYZ,
>  and b) how much benefit is there from going to more than three 
> color primaries for the device-independent space.

a) not much
b) more than 3 primaries would present some mathematical difficulties 
(N->1->N mappings anybody?)


Chris