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Mismatch between VFB and Saved file

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  • Mismatch between VFB and Saved file

    Hi,

    I keep getting less saturated and generally a color difference between the image i see in the VFB and the saved image (or its clone inside max)

    Can't show this thing since even screen capture results the same way when inserted into an image editing application.

    Hope someone can help me get around this very annoying thing
    sigpic

  • #2
    Do you have the gamma correction settings enabled in 3ds Max? Are you using the sRGB button in the V-Ray VFB?

    Best regards,
    Vlado
    I only act like I know everything, Rogers.

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    • #3
      Hi Vlado,

      Yes and yes. Max gamma is enabled at 2.2 and this is also the value for input and output.
      I'm attaching a reference image (this time the screen capture did get the colors is see in the VFB that are more vivid the the saved version)

      I used selective strip masking to show the difference in color in some areas of the image :



      I've also tested with the Don't Affect colors switch OFF and turned off the sRGB button in the VFB... the result was the same less vivid image during render view and saved version too.
      sigpic

      Comment


      • #4
        You should not have it in output. Only input should havegamma set at 2.2. AFAIK.

        Comment


        • #5
          But then, the image is saved very dark and not like it shows on the VFB. i understand that the sRGB button doesn't take any effect in the saving process, so how do i get the same image on screen into a jpg file?
          sigpic

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          • #6
            You either need to set your color mapping gamma to 2.2 or set teh curve properly in the VFB (thats the old method tho) so just put 2.2 in the gamma in your vray: color mapping.

            Comment


            • #7
              What is probably going on is that the sRGB color space is similar, but not the same, as a 2.2 gamma transformation, especially in the dark colors. That's why you can't get the exact same result with just an output gamma of 2.2. Working with LUT profiles might work better, but I don't know how this is set up.

              Like DaForce suggested, you can just use the color mapping gamma at 2.2, with "don't affect colors" off, and turn off the 3ds Max output gamma - the result should be the same, since the Output gamma of 3ds Max bakes the gamma correction into the output image too.

              Best regards,
              Vlado
              Last edited by vlado; 15-01-2008, 03:29 AM.
              I only act like I know everything, Rogers.

              Comment


              • #8
                We use the Color Mapping Gamma of 2.2 as well, but then the colours are all washed out. So we then use the ColorCorrect plugin and set the Gamma back to 2.2 so the materials become darker.
                Is that the proper way to do it? Because the whole LWF story is still something I barely understand.

                -edit-
                Also, the materials in my material editor turn up really dark. Is there a way to make them appear lighter? By turning on "Enable Gamma/LUT Correction" and checking "Affect Material Editor"?
                Last edited by DrJan; 15-01-2008, 04:33 AM.
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                • #9
                  Are you using Photoshop to view and save the screen buffers? Maybe it is applying some weird color profile?
                  Eric Boer
                  Dev

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                  • #10
                    Originally posted by RErender View Post
                    Are you using Photoshop to view and save the screen buffers? Maybe it is applying some weird color profile?
                    It looks the same in all viewers. I just can't seem to have the exact VFB + sRGB image saved to file... only Screen capture shows those colors, and i did test with max gamma off and don't affect colors off... all the same.

                    The best method so far is using a custom curve inside the VFB to adjust for what the sRGB button does automatically. the result is then burnt into the saved image... but it's not that good of a method if consistent results is what I'm looking for.

                    Cheers
                    sigpic

                    Comment


                    • #11
                      bakbek - got photoshop? work in linear space, don't bake the gamma into the image, view it in sRGB in the VFB, save to EXR, open in photoshop - same image as in VFB with sRGB on...

                      Comment


                      • #12
                        Originally posted by sv View Post
                        bakbek - got photoshop? work in linear space, don't bake the gamma into the image, view it in sRGB in the VFB, save to EXR, open in photoshop - same image as in VFB with sRGB on...
                        did that... but still, not the same
                        i'll try all this on a new scene, fresh from the start, just to eliminate any kind of human error along the way.
                        sigpic

                        Comment


                        • #13
                          bakbek, make sure your setup looks like this:



                          I suspect your output setup with 2.2 is doing something odd to the saving process.

                          then the image opened in photoshop will be exactly the same as in the VFB. As Vlado points out, Gamma 2.2 and sRGB are not quite the same, but very close. I *think* the .exr format applies the sRGB curve to it's linearly stored data.

                          make sure your using linear colour mapping, and just to be sure save the .exr from the VFB.

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                          • #14
                            did exactly what u suggested... but the same result. what do i do wrong here?
                            sigpic

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                            • #15
                              i think you need to provide more information; it'd be helpful to at least show us some settings! you've obviously got something different / wrong somewhere along the line - if you've done this as above your renders will look the same. I do this day in, day out, everyday - It's the only setup i use - my renders look exactly the same in the VFB as they do in Photoshop & other post applications. See these images:

                              1. VFB with sRGB


                              2. rendered .exr opened in photoshop


                              3. layered in Photoshop with 'difference' blending - i.e. a result of 0 for each pixel, i.e. exactly the same image.

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