Again, Photoshop is a straight color application - there is no such thing as color values when the opacity is zero.
PNG is also well defined in it's behavior - and behaves exactly as the file format specification says it must. TIFF can support alpha channels (which can contain anything) AND transparency/opacity channels. It sounds like you have these confused. Chris On 6/5/09 10:14 AM, "[email protected]" <[email protected]> wrote: 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 rendered 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 color of the clouds in the sky). If I use the default EXR plugin in CS4 it creates an RGB/32 document, 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 alter the way it deals with the alpha, and I have the choice to ignore the alpha 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 example also discards all color data where the alpha is 0.0. The TIFF plugin 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 PNG/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 love an option in the main program settings that globally modified how all image 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 channel 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. The two problems I have with this plugin is that; 1) It creates an RGB/16 document instead of a RGB/32 which clamps the RGB values and leaves me stuck 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 it 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" <[email protected]> To: [email protected], [email protected] 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 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 ======================================================== _______________________________________________ Openexr-user mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/openexr-user
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