[Openexr-user] Photoshop Plugin importing as RGB/16 bit

"Chris Cox" <ccox@ado= be.com</a>>

1970-01-01 00:00:00 UTC

<title>Re: [Openexr-user] Photoshop Plugin importing as RGB/16 bit</title>

Again, Photoshop=
is a straight color application =E2=80=93 there is no such thing as color =
values when the opacity is zero. 
 
PNG is also well defined in it=E2=80=99s behavior =E2=80=93 and behaves exa=
ctly as the file format specification says it must. 
TIFF can support alpha channels (which can contain anything) AND transparen=
cy/opacity channels.  It sounds like you have these confused. 
 
Chris 
 
  
 
 
On 6/5/09 10:14 AM, "<a href=3D"***@nc3d.com" target=3D"_blank">***@nc3d.co=
m</a>" <<a href=3D"***@nc3d.com" target=3D"_blank">***@nc3d.com</a>> =
wrote: 
 
<blockquote><=
span style=3D"font-size: 12pt;">Hi Chris, 
  Maybe I didn't explain this well enough.  There really is =
a couple of issues here.  So to explain further, I have an EXR file re=
ndered out of 3DStudio in a HDR scene.  The scene is a landscape with =
buildings, hills, and a sky.  The hills and buildings have an alpha of=
1.0, the sky has an alpha of 0.0.  The RGB information is not limited=
to a 0.0 - 1.0 range...  there are some color values that go up into =
the 5.0-8.0 range (for example bright reflections on the windows, and the c=
olor of the clouds in the sky). 
 
  If I use the default EXR plugin in CS4 it creates an RGB/32 doc=
ument, but the sky comes in 100% transparent.  This is great if I don'=
t need the sky, but there is color data for the sky in the EXR file.  =
The sky is blue and there are white clouds.  In After Effects I can al=
ter the way it deals with the alpha, and I have the choice to ignore the al=
pha if I so choose. In Photoshop there are no options to do this.  The=
EXR plugin is not the only one that does this.  The PNG plugin for ex=
ample also discards all color data where the alpha is 0.0.  The TIFF p=
lugin on the other hand puts the alpha information into a sepperate channel=
.  I can then choose to use that alpha however I wish.  Sometimes=
it's nice to have the alpha pre-composited with the RGB data the way the P=
NG/EXR plugin works, but it would also be nice to have an option somewhere =
that modifies how Photoshop deals with alpha in an image.  I would lov=
e an option in the main program settings that globally modified how all ima=
ge importers dealt with the Alpha. 
 
  Now if I use the plugin on the OpenEXR website, it brings up a =
dialog where I can choose to Un-Premultiply, I can change the Gamma, and I =
can alter the Exposure.  It also places the alpha into a sepperate cha=
nnel like the way the TIFF plugin works.  I can see my sky and I have =
my alpha in a sepperate channel so that I can do with it what I please. &nb=
sp;The two problems I have with this plugin is that; 1) It creates an RGB/1=
6 document instead of a RGB/32 which clamps the RGB values and leaves me st=
uck with the gamma/exposure settings I selected during import, and 2) There=
is no 64bit version of the plugin. 
 
  To recap, the default EXR plugin needs a user control for how i=
t deals with the alpha, and the OpenEXR plugin needs to open the image as a=
RGB/32 so that it does not clamp the color values. 
 
I hope this posting is more clear. 
 
-Ray 
 
----- Original Message ----- 
From: "Chris Cox" <<a href=3D"***@adobe.com" target=3D"_blank">***@ado=
be.com</a>> 
To: <a href=3D"***@nc3d.com" target=3D"_blank">***@nc3d.com</a>, <a href=3D=
"openexr-***@nongnu.org" target=3D"_blank">openexr-***@nongnu.org</a> 
Sent: Thursday, June 4, 2009 6:37:24 PM GMT -08:00 US/Canada Pacific 
Subject: Re: [Openexr-user] Photoshop Plugin importing as RGB/16 bit 
 
Re: [Openexr-user] Photoshop Plugin importing as RGB/16 bit <=
/font>Ray; 
 
Photoshop is a straight color application, and OpenEXR is defined as being =
premultiplied.  This means that OpenEXR data has to be un-multiplied b=
y 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 =E2=80=9CA=E2=80=9D channel (defined in t=
he spec as opacity/transparency data) correctly =E2=80=93 it opens it as op=
acity/transparency. 
What the Photoshop EXR plugin does not do is give you a way to open the tra=
nsparency channel as an arbitrary alpha channel, or to open channels other =
than RGBA. 
 
I=E2=80=99m sorry I don=E2=80=99t have a solution for you, but your post so=
unded like you were confused about the terminology and what was happening t=
o your data (enough so that I still don=E2=80=99t know what=E2=80=99s not w=
orking for you with the Photoshop EXR plugin). 
 
Chris 
 
 
 
On 6/4/09 4:23 PM, "<a href=3D"***@nc3d.com" target=3D"_blank">***@nc3d.com= </a>" <<a href=3D"***@nc3d.com" target=3D"_blank">***@nc3d.com</a>> w=
rote: 
 
<blockquote>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 Effe=
cts in a 32 bit floating point composite and it's all working fine.  T=
he problem I'm having is that I also need to composite some scenes in Photo=
shop 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. &nbsp=
;Thankfully it knows how to handle the alpha channel properly, but unfortun=
ately the plugin imports the image into a 16bit integer document and any va=
lue above 1.0 is clipped.  I can't use the exposure adjustment to acce=
ss the over bright details.  Because of these import problems I have t=
o 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 v=
ersion that imports images into a 32bit document and maintain the full colo=
r range, or provide exposure controls in the plugin?  Also, I could us=
e a 64bit version of the plugin for the 64bit version of Photoshop. 
 
Thanks, 
  Ray Collett 
 
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--=3D=3D--           &nbs=
p;     Ray Collett      &=
nbsp;         --=3D=3D-- 
Technical Director; Newlands & Company Inc. www.nc3d.com 
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nbsp;         --=3D=3D-- 
Technical Director; Newlands & Company Inc. www.nc3d.com 
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