[Openexr-devel] Re: Openexr-devel Digest, Vol 18, Issue 6

[Tom Dilligan]

> Date: Wed, 09 Jun 2004 10:33:03 +0100
> From: Ken McGaugh <address@hidden>
> Subject: [Openexr-devel] exchanging exr's
> To: address@hidden
> Message-ID: <address@hidden>
> Content-Type: text/plain; charset=us-ascii; format=flowed
> 
> Hello all,
> 
> We have recently shifted most of our pipeline (both 3D and 2D) to OpenEXR
> format, and we will soon be sending exr's to Cinesite UK for filmout.
> Keven Wheatly from Cinesite and I have worked out a spec for exchanging
> these exr's, but we hope this can become a standard.  Below is the the
> proposed spec, and we would appreciate comments and suggestions.
> 

[cut]

> All the attributes are of type V3fAttribute and are listed below
> with the default values to be assumed if the attribute is not
> present in the file.
> 
>      pdxBlackPoint            = {0, 0, 0}
>      pdxWhiteReference        = {685, 685, 685}
>      pdxNegativeGamma         = {0.6, 0.6, 0.6}
>      pdxDensityPerCodeValue   = {0.002, 0.002, 0.002}

[cut]


I would suggest that the pdxBlackPoint, pdxWhiteReference, be stored as
floating point values, and that the pdxDensityPerCodeValue be dropped.

Since the EXR format supports floating point numbers, there is no
particular reason that we need to continue to hedge to the cineon/dpx
method of encoding the floating point density values.

This would change the common black and white points to .19 (a code value
of 95) and 1.37 (a code value of 685). 

>>>Tom