Ray;

Photoshop is a straight color application, and OpenEXR is defined as being 
premultiplied.  This means that OpenEXR data has to be un-multiplied by the 
transparency/opacity values to work in Photoshop.  To a straight color 
application, there is no meaning to color values when the opacity is zero.  If 
the opacity is non-zero, then the color values are there -  just un-multiplied 
so they will composite correctly.

Photoshop already handles the EXR "A" channel (defined in the spec as 
opacity/transparency data) correctly - it opens it as opacity/transparency.
What the Photoshop EXR plugin does not do is give you a way to open the 
transparency channel as an arbitrary alpha channel, or to open channels other 
than RGBA.

I'm sorry I don't have a solution for you, but your post sounded like you were 
confused about the terminology and what was happening to your data (enough so 
that I still don't know what's not working for you with the Photoshop EXR 
plugin).

Chris



On 6/4/09 4:23 PM, "[email protected]" <[email protected]> wrote:

I'm working on a project that is rendering 32bit floating bit EXR files out of 
3DStudio.  I'm then compiling these frames in After Effects in a 32 bit 
floating point composite and it's all working fine.  The problem I'm having is 
that I also need to composite some scenes in Photoshop CS4, and the default 
Photoshop EXR plugin is tossing out any data from the image that has a 
transparent alpha.  I found the Photoshop plugin on the OpenEXR website and had 
hopes that it would do what I needed.  Thankfully it knows how to handle the 
alpha channel properly, but unfortunately the plugin imports the image into a 
16bit integer document and any value above 1.0 is clipped.  I can't use the 
exposure adjustment to access the over bright details.  Because of these import 
problems I have to run each image through After Effects and do the exposure 
processing there, then export an image to Photoshop.

Can the maintainer of the OpenEXR photoshop plugin please recompile a new 
version that imports images into a 32bit document and maintain the full color 
range, or provide exposure controls in the plugin?  Also, I could use a 64bit 
version of the plugin for the 64bit version of Photoshop.

Thanks,
  Ray Collett

--
========================================================
--==--                 Ray Collett                --==--
Technical Director; Newlands & Company Inc. www.nc3d.com
========================================================


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