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Re: Fwd: White Balance in Panoramas

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  • panovrx
    ... Color correction is an area of active research and new technologies are emerging regularly -- so there are a plethora of thirdparty plugins for this some
    Message 1 of 23 , Feb 29, 2008
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      --- In PanoToolsNG@yahoogroups.com, "Nelson Mendes" <nmendes@...> wrote:
      >
      > Hi, I work mainly with indoor panoramas, and what's been really a time
      > consuming effort in the creation of the panoramas is the white balance
      > compensation.
      >

      Color correction is an area of active research and new technologies are
      emerging regularly -- so there are a plethora of thirdparty plugins for
      this some of which are superior I think to anything in Photoshop. The
      recently announced Viveza plugin from Nik Efex looks particularly
      interesting ...
      http://www.niksoftware.com/viveza/en/entry.php?
      view=intro/viveza_announcement.shtml

      Peter
    • William Donelson
      I prepared a hardback 8x11 notebook (with 100 pages of lined note paper) for colour balance & correction: I went to a charity shop, and bought an old black
      Message 2 of 23 , Mar 1, 2008
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        I prepared a hardback 8x11 notebook (with 100 pages of lined note paper) for colour
        balance & correction:

        I went to a charity shop, and bought an old black velvet dress to cut up for patches.

        I glued several pieces of the black velvet (with the "grain" in various directions) into the
        front cover. Now, when the camera sees it, some of the patches look dark black, and
        some look gray. The lined note paper looks white.

        You can also arranged for the front cover to be "in the shade" (of itself or of some other
        shadow) to get an even darker set of blacks.

        This gives us a very good range of blacks, grays and whites to use in Photoshop
        correction.

        And, the notepaper can be used to mark down info about the shot.


        Cheers
        William



        --- In PanoToolsNG@yahoogroups.com, Eric O'Brien <ericob@...> wrote:
        >
        > I have been including a neutral "gray"("grey") target every time I
        > shoot a panorama, for quite a while. Certainly in many artificial
        > (architectural) situations it can be difficult to find a *true*
        > neutral in the scene after the fact! (Whatever you click on with
        > Photoshop's "neutral picker" produces a horrible result.)
        >
      • Snowy Aldon
        Hi All, any colour balance work requires a spectrally neutral target to balance from. One which has little or no florescent materials. The targets that William
        Message 3 of 23 , Mar 1, 2008
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          Hi All,

          any colour balance work requires a spectrally neutral target to
          balance from. One which has little or no florescent materials.

          The targets that William has suggested would work well for tonal
          adjustments but will almost certainly give colour casts under most
          conditions.

          >>
          >> I prepared a hardback 8x11 notebook (with 100 pages of lined note
          >> paper) for colour
          >> balance & correction:
          >>
          >> I went to a charity shop, and bought an old black velvet dress to
          >> cut up for patches.
          >>
          >> I glued several pieces of the black velvet (with the "grain" in
          >> various directions) into the
          >> front cover. Now, when the camera sees it, some of the patches
          >> look dark black, and
          >> some look gray. The lined note paper looks white



          It is best to use a calibrated target like a macbeth chart or a QP card.

          The placement of the target in the scene is very critical. In the
          example being used of the room lit with tungsten balanced lighting
          and also getting light from a window. the closer the neutral target
          is placed to the lamp the more tungsten light and the bluer the
          daylight and vice versa.

          The same effect will be present in a landscape. If the target is
          fully illuminated by the sun it will give a different result than in
          the shade.

          If you are on a lawn and the target is backlit so no sunlight is
          falling on the target and it is shaded from the blue sky, a major
          source of illumination will be bright green light from the lawn. If
          this is then used to "neutralise" the images a magenta cast will
          almost certainly be introduced.

          In the case of VR Panoramas one must "correct" the image so that it
          appears a faithful representation of the scene captured ( on a
          profiled monitor). This of course forms an integral part of the
          creative process. Relying on a mechanical approach to white balance
          of digital will not give the best results. these targets and useful
          guides when not used in the studio.

          Hope this helps


          best

          Snowy





          On 1 Mar 2008, at 13:33, William Donelson wrote:

          > .
          >
          > You can also arranged for the front cover to be "in the shade" (of
          > itself or of some other
          > shadow) to get an even darker set of blacks.
          >
          > This gives us a very good range of blacks, grays and whites to use
          > in Photoshop
          > correction.
          >
          > And, the notepaper can be used to mark down info about the shot.
          >
          > Cheers
          > William
          >



          [Non-text portions of this message have been removed]
        • William Donelson
          ... Yes, you do have to be careful, and aware of reflections and other light sources, as you mention. But the technique I outlined has given us the best
          Message 4 of 23 , Mar 4, 2008
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            --- In PanoToolsNG@yahoogroups.com, Snowy Aldon <lists@...> wrote:
            > The targets that William has suggested would work well for tonal
            > adjustments but will almost certainly give colour casts under most
            > conditions.
            Yes, you do have to be careful, and aware of reflections and other light sources, as you
            mention.

            But the technique I outlined has given us the best results we've had in 15 years of doing
            panoramas.

            Properly used, it never gives colour casts, or false colours, except in extreme circumstances.

            We tried using colour charts and grayscale charts, but these were essentially useless, as they
            are far too dependent on the lighting conditions.

            The "best black" can be achieved by building a box, lined with black velvet, and open on
            one side, so that the interior is completely unlit. But, we have found this to be unnecessary,
            except in unusual circumstances.
          • Snowy Aldon
            Hi, I m really interested in this technique. The comments we re made as an extrapolation of colour management in the studio and on location. I have been using
            Message 5 of 23 , Mar 4, 2008
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              Hi,

              I'm really interested in this technique.

              The comments we're made as an extrapolation of colour management in
              the studio and on location. I have been using various method and
              targets with some success.

              It seems strange that the velvet gives a neutral value when
              illuminated to be in the mid-tone. I would have have supposed that
              the colour bias of the dyes would become apparent and introduce a cast.

              Do you colour balance/correct/neutralise to the velvet and adjust the
              images to give an equal RGB value grey? And how does achieving a
              truly "black" black give any information regarding the colour balance
              of the image?

              TIA

              Snowy

              On 4 Mar 2008, at 14:53, William Donelson wrote:



              >> --- In PanoToolsNG@yahoogroups.com, Snowy Aldon <lists@...> wrote:
              >> > The targets that William has suggested would work well for tonal
              >> > adjustments but will almost certainly give colour casts under most
              >> > conditions.
              >> Yes, you do have to be careful, and aware of reflections and other
              >> light sources, as you
              >> mention.
              >>
              >> But the technique I outlined has given us the best results we've
              >> had in 15 years of doing
              >> panoramas.
              >>
              >> Properly used, it never gives colour casts, or false colours,
              >> except in extreme circumstances.
              >>
              >> We tried using colour charts and grayscale charts, but these were
              >> essentially useless, as they
              >> are far too dependent on the lighting conditions.
              >>
              >> The "best black" can be achieved by building a box, lined with
              >> black velvet, and open on
              >> one side, so that the interior is completely unlit. But, we have
              >> found this to be unnecessary,
              >> except in unusual circumstances.
              >


              [Non-text portions of this message have been removed]
            • William Donelson
              ... You have to be careful which patch of velvet you use. Some are not black. ... We do not use the box-of-velvet anymore, as our 4 patches of velvet at
              Message 6 of 23 , Mar 4, 2008
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                --- In PanoToolsNG@yahoogroups.com, Snowy Aldon <lists@...> wrote:
                > It seems strange that the velvet gives a neutral value when
                > illuminated to be in the mid-tone. I would have have supposed that
                > the colour bias of the dyes would become apparent and introduce a cast.

                You have to be careful which patch of velvet you use. Some are not black.

                > Do you colour balance/correct/neutralise to the velvet and adjust the
                > images to give an equal RGB value grey? And how does achieving a
                > truly "black" black give any information regarding the colour balance
                > of the image?

                We do not use the box-of-velvet anymore, as our "4 patches of velvet" at different
                orientations works very well. Some of the patches look blacker than others, and some can
                be used as gray-level samples.

                Having an in-scene black is useful if you are shooting on film (as we usually do - Seitz
                Super Roundshot 220).

                Having specular (over-exposed) white patches are not useful, so we use a variety of
                techniques in Photoshop to set the top white level.

                In the end, the velvet-patches are a short-cut to getting NEAR to correct colour, and we
                use Photoshop to adjust the colour to "Correct" levels by eye and memory.

                Hope this helps.
              • Rik Littlefield
                ... Using black velvet this way is a very clever trick. What happens, I believe, is that the gray appearance is caused by a myriad of specular reflections
                Message 7 of 23 , Mar 4, 2008
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                  --- In PanoToolsNG@yahoogroups.com, "William Donelson" <wd@...> wrote:
                  >
                  > --- In PanoToolsNG@yahoogroups.com, Snowy Aldon <lists@> wrote:
                  > > It seems strange that the velvet gives a neutral value when
                  > > illuminated to be in the mid-tone. I would have have supposed
                  > > that the colour bias of the dyes would become apparent
                  > > and introduce a cast.
                  >
                  > You have to be careful which patch of velvet you use.
                  > Some are not black.
                  >
                  > > Do you colour balance/correct/neutralise to the velvet
                  > > and adjust the images to give an equal RGB value grey?
                  > > And how does achieving a truly "black" black give any
                  > > information regarding the colour balance
                  > > of the image?
                  >
                  > We do not use the box-of-velvet anymore, as our
                  > "4 patches of velvet" at different orientations
                  > works very well. Some of the patches look blacker
                  > than others, and some can be used as gray-level samples.

                  Using black velvet this way is a very clever trick. What happens, I
                  believe, is that the "gray" appearance is caused by a myriad of
                  specular reflections from the surfaces of the fibers. Specular
                  reflections are always non-colored, so indeed this method should
                  produce a very neutral gray as long as the body of the fibers is very
                  dark in comparison.

                  --Rik
                • johncharlesriley
                  ... Sorry, I have to jump in here. I am not sure what you might be thinking of, but specular reflections have the same color as the incident light. When you
                  Message 8 of 23 , Mar 7, 2008
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                    >
                    > Using black velvet this way is a very clever trick. What happens, I
                    > believe, is that the "gray" appearance is caused by a myriad of
                    > specular reflections from the surfaces of the fibers. Specular
                    > reflections are always non-colored, so indeed this method should
                    > produce a very neutral gray as long as the body of the fibers is very
                    > dark in comparison.
                    >
                    > --Rik
                    >

                    Sorry, I have to jump in here. I am not sure what you might be thinking of, but specular
                    reflections have the same color as the incident light. When you see yourself in a mirror,
                    that is a specular reflection. A specular reflection is simply when light is reflected in a
                    mirror-like fashion from a smooth surface. Examples are the glare off of a car (or water
                    or snow) from the sun. They are problematic because you are seeing a reflection of the
                    sun and not the object itself. Since specular reflections are partially polarized (or
                    completely if at Brewster's angle), polarized sunglasses can drastically reduce their
                    intensity. Then you can see the object itself by the diffusely reflected light, which is
                    scattered in all directions.

                    Sorry for being pedantic, but I am a physics professor and just can't help it 8-) Now, what
                    else might be going on with the fibers of black velvet, I don't know, but it could be
                    interesting to hear.

                    John
                  • Georgia Real Tours
                    ... Exactly. The grain of the fabric acts as a rudimentary polarization filter. Further, since it is diffuse, the light reflected is a culmination of the
                    Message 9 of 23 , Mar 8, 2008
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                      On 3/7/08, johncharlesriley <johnriley@...> wrote:
                      > >
                      > > Using black velvet this way is a very clever trick. What happens, I
                      > > believe, is that the "gray" appearance is caused by a myriad of
                      > > specular reflections from the surfaces of the fibers. Specular
                      > > reflections are always non-colored, so indeed this method should
                      > > produce a very neutral gray as long as the body of the fibers is very
                      > > dark in comparison.
                      > >
                      > > --Rik
                      > >
                      >
                      > Sorry, I have to jump in here. I am not sure what you might be thinking of, but specular
                      > reflections have the same color as the incident light. When you see yourself in a mirror,
                      > that is a specular reflection. A specular reflection is simply when light is reflected in a
                      > mirror-like fashion from a smooth surface. Examples are the glare off of a car (or water
                      > or snow) from the sun. They are problematic because you are seeing a reflection of the
                      > sun and not the object itself. Since specular reflections are partially polarized (or
                      > completely if at Brewster's angle), polarized sunglasses can drastically reduce their
                      > intensity. Then you can see the object itself by the diffusely reflected light, which is
                      > scattered in all directions.
                      >
                      > Sorry for being pedantic, but I am a physics professor and just can't help it 8-) Now, what
                      > else might be going on with the fibers of black velvet, I don't know, but it could be
                      > interesting to hear.

                      Exactly. The grain of the fabric acts as a rudimentary polarization
                      filter. Further, since it is diffuse, the light reflected is a
                      culmination of the ambient light in the room. The average of all
                      those random specular reflections is what is sought.

                      But you knew that and were just testing us! Very tricky, Mr. Riley,
                      but it's turtles all the way down!

                      ;c)

                      R~


                      --
                      Mid GA: 478-599-1300
                      ATL: 678-438-6955
                      garealtours.com
                    • Ken Warner
                      I get that :-) Georgia Real Tours wrote: [stuff deleted] Very tricky, Mr. Riley, but it s turtles all the way down!
                      Message 10 of 23 , Mar 8, 2008
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                        I get that :-)

                        Georgia Real Tours wrote:
                        [stuff deleted]

                        Very tricky, Mr. Riley, but it's turtles all the way down!
                      • Rik Littlefield
                        ... Yes, exactly. Previous writers were concerned about the color of the fibers producing something other than a non-neutral gray. When I wrote that the
                        Message 11 of 23 , Mar 8, 2008
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                          --- In PanoToolsNG@yahoogroups.com, "johncharlesriley"
                          <johnriley@...> wrote:
                          >
                          > >
                          > > Using black velvet this way is a very clever trick.
                          > > What happens, I believe, is that the "gray" appearance
                          > > is caused by a myriad of specular reflections
                          > > from the surfaces of the fibers. Specular
                          > > reflections are always non-colored, so indeed
                          > > this method should produce a very neutral gray
                          > > as long as the body of the fibers is very
                          > > dark in comparison.
                          > >
                          > > --Rik
                          > >
                          >
                          > Sorry, I have to jump in here. I am not sure what
                          > you might be thinking of, but specular reflections
                          > have the same color as the incident light.

                          Yes, exactly. Previous writers were concerned about the color of the
                          fibers producing something other than a non-neutral gray. When I
                          wrote that the reflection was "non-colored", what I meant was that
                          the color of the reflected light would not be altered by the color of
                          the underlying fiber, so the myriad of specular reflections taken
                          together would act like a neutral gray diffuse reflector. Sorry I
                          did not use enough words to make that completely clear.

                          --Rik
                        • Georgia Real Tours
                          ... Oops, my bad. You used enough words; I just failed to use all of them. Kinda makes a difference when you get em all rounded up. :c R~ -- Mid GA:
                          Message 12 of 23 , Mar 10, 2008
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                            On 3/9/08, Rik Littlefield <rj.littlefield@...> wrote:
                            >
                            > --- In PanoToolsNG@yahoogroups.com, "johncharlesriley"
                            > <johnriley@...> wrote:
                            > >
                            > > >
                            > > > Using black velvet this way is a very clever trick.
                            > > > What happens, I believe, is that the "gray" appearance
                            > > > is caused by a myriad of specular reflections
                            > > > from the surfaces of the fibers. Specular
                            > > > reflections are always non-colored, so indeed
                            > > > this method should produce a very neutral gray
                            > > > as long as the body of the fibers is very
                            > > > dark in comparison.
                            > > >
                            > > > --Rik
                            > > >
                            > >
                            > > Sorry, I have to jump in here. I am not sure what
                            > > you might be thinking of, but specular reflections
                            > > have the same color as the incident light.
                            >

                            > together would act like a neutral gray diffuse reflector. Sorry I
                            > did not use enough words to make that completely clear.


                            Oops, my bad. You used enough words; I just failed to use all of
                            them. Kinda makes a difference when you get 'em all rounded up. :c\

                            R~


                            --
                            Mid GA: 478-599-1300
                            ATL: 678-438-6955
                            garealtours.com
                          • Luca Vascon
                            I simply use a white plastic drinking cup. One of those very cheap ones you buy at supermarket. I put it in front of the lens with transparent tape. I shoot
                            Message 13 of 23 , Mar 10, 2008
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                              I simply use a white plastic drinking cup.
                              One of those very cheap ones you buy at supermarket.
                              I put it in front of the lens with transparent tape.
                              I shoot one picture against main lightsource, completely out of focus.
                              Like it was taking incident light.
                              I make white on that.
                              Those things are made of a plastic whose physical propreiety is also to
                              be... perfectly white.
                              If you fisheye-shoot one from inside you have a kind of light dome of
                              all light sources and principal chrominance of light reflection.
                              You don't need anything else.

                              Georgia Real Tours ha scritto:
                              >
                              > On 3/9/08, Rik Littlefield <rj.littlefield@...
                              > <mailto:rj.littlefield%40computer.org>> wrote:
                              > >
                              > > --- In PanoToolsNG@yahoogroups.com
                              > <mailto:PanoToolsNG%40yahoogroups.com>, "johncharlesriley"
                              > > <johnriley@...> wrote:
                              > > >
                              > > > >
                              > > > > Using black velvet this way is a very clever trick.
                              > > > > What happens, I believe, is that the "gray" appearance
                              > > > > is caused by a myriad of specular reflections
                              > > > > from the surfaces of the fibers. Specular
                              > > > > reflections are always non-colored, so indeed
                              > > > > this method should produce a very neutral gray
                              > > > > as long as the body of the fibers is very
                              > > > > dark in comparison.
                              > > > >
                              > > > > --Rik
                              > > > >
                              > > >
                              > > > Sorry, I have to jump in here. I am not sure what
                              > > > you might be thinking of, but specular reflections
                              > > > have the same color as the incident light.
                              > >
                              >
                              > > together would act like a neutral gray diffuse reflector. Sorry I
                              > > did not use enough words to make that completely clear.
                              >
                              > Oops, my bad. You used enough words; I just failed to use all of
                              > them. Kinda makes a difference when you get 'em all rounded up. :c\
                              >
                              > R~
                              >
                              > --
                              > Mid GA: 478-599-1300
                              > ATL: 678-438-6955
                              > garealtours.com
                              >
                              >
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