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32bit Vs 16bit compositing

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  • 32bit Vs 16bit compositing

    If you've seen my other recent thread, you will read that I've been messing about with creating a composite image in Photoshop from the various render elements.

    I have discovered one significant issue. You may well be aware of it, and I am probably being slow, but we use Photoshop CS2. This does not allow multi layered 32bit images to be built. CS3 does. When I build an image in a demo of CS3, I get an exact match between the RGB render (as seen in the VFB) and the added (linear dodge) GI, Lighting, Reflection and Specular elements. It is perfect.

    In CS2, I must reduce each of the EXRs from 32bit to 16bit before I can begin to layer them up. The result is that the combined layers are quite a bit different from the RGB render. In the simple scene in which I am working, the 16bit version is quite a bit lighter, and the reflections are all brighter.

    To test the theory, I converted the layered 32bit file in CS3 down to 16bit and I get the same inconsistency between the layered and the straight RGB version.

    This is a pain in the butt as we use CS2 having seen no significant reason to upgrade lately. If we decide to go down the composite image route, it would obviously be a good reason to upgrade, however, I was wondering how many of you out there are working with 32bit compositions. In my limited past experience in working with layered 16bit compositions, I found the overall Photoshop pipeline much slower to work with: bigger files and generally much slower refresh rates when zooming around a 4k+ pixel image.

    Is their mileage in the 32bit route, or do you use a more complex pipeline where the 'base composite render' is constructed in one 32bit Photoshop file, but then it is 'flattened' into an 8bit or 16bit file for further PP work (adding people/vegetation etc)?
    Kind Regards,
    Richard Birket
    ----------------------------------->
    http://www.blinkimage.com

    ----------------------------------->

  • #2
    Sorry, just re-read your post after posting this and realised I had the wrong end of the stick!
    Last edited by stef.thomas; 03-12-2009, 05:50 AM. Reason: Irrelevant
    Check out my models on 3dOcean

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    • #3
      You are right that flattening helps in the conversion. I would think that this is because the dodge layers use a lot more 'data' to work their adjustments when they are seperate.
      Kind Regards,
      Richard Birket
      ----------------------------------->
      http://www.blinkimage.com

      ----------------------------------->

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      • #4
        You must've got that before I edited it, apologies for ruining the continuity of the thread! I guess it wasn't as irrelevant as I thought
        Check out my models on 3dOcean

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        • #5
          Am on cs 4 with no change
          photoshop sucks for dealing with 32 bit
          I have been remaking the rgb in 32 bit do some basic exposure adjustments then flatten the image and converting straight to 8 bit and work up the image in 8 bit

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          • #6
            Originally posted by pg1 View Post
            Am on cs 4 with no change
            photoshop sucks for dealing with 32 bit
            I have been remaking the rgb in 32 bit do some basic exposure adjustments then flatten the image and converting straight to 8 bit and work up the image in 8 bit
            CS3 allows you to have 32bit compositions. Doesn't CS4?
            Kind Regards,
            Richard Birket
            ----------------------------------->
            http://www.blinkimage.com

            ----------------------------------->

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            • #7
              I am also on CS3 and cannot use layers with 32bit images. Tricky, how are you able to do that? What am I missing? Thanks

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              • #8
                Originally posted by voltron7 View Post
                I am also on CS3 and cannot use layers with 32bit images. Tricky, how are you able to do that? What am I missing? Thanks
                Think you need CS3 extended.
                Kind Regards,
                Richard Birket
                ----------------------------------->
                http://www.blinkimage.com

                ----------------------------------->

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                • #9
                  I'm on CS3 as well and 32bit layers work just fine. I didn't do anything special to get that though - it just works that way so I'm not sure what the problem is. EDIT:Tricky is probably right about the extended thing...

                  For the 16bit vs. 32bit composite, keep in mind that the 32bit color space is Linear sRGB while the 16bit colorspace is probably sRGB (i.e. not a linear space). You can get around this by setting the "blend RGB colors using gamma..." to 1.0 in the color setting. You additionally should get a linear RGB color space for 8/16bit images and assign it to the image. Even with these steps I've never gotten the 16bit and 32 bit to match up exactly. They're pretty close however, much closer than if you don't take the above steps.

                  BTW-this is much easier (colorspace that is) in after effects. Under Project Settings-->Color Settings select a working space and then check "Linearize working space". 8/16/32 all match each other and match the RGB values from the 32bit photoshop file.
                  www.dpict3d.com - "That's a very nice rendering, Dave. I think you've improved a great deal." - HAL9000... At least I have one fan.

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                  • #10
                    both cs3 and cs 4 have to be the extended versions to do layered 32bit work. CS4 still treats the alpha as transparency even with ProEXR. There have been massive protests to adobe. But the guy who writes the format I/O business believes strongly that the EXR spec calls for the alpha to be read as transparent... Join the fun

                    http://forums.adobe.com/thread/369637?start=0&tstart=0

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                    • #11
                      The problem is as tricky stated at the start of the thread

                      "In CS2, I must reduce each of the EXRs from 32bit to 16bit before I can begin to layer them up. The result is that the combined layers are quite a bit different from the RGB render"

                      and what I meant was that the problem is still the same in Cs 4

                      Hey Jonahhawk I saw that thread a while back, it gets quiet heated for a while, but chris coxs seems to back off a bit in the end so hopefully they will sort it out
                      In the mean time you can copy the openexr.8bi file from the file format folder of Cs2 across to Cs 3 and Cs4 (backup first and you will get your background back in your exr
                      it doesnt work for Cs 4 64 bit

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