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Re: [PanoToolsNG] Fwd: White Balance in Panoramas

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  • Shawn Steigner
    I use a color(or level) adjustment layer in Photoshop. Adding a corrective blue layer for the indoor lights. Then using the a mask on this layer to hide where
    Message 1 of 23 , Feb 28, 2008
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      I use a color(or level) adjustment layer in Photoshop.
      Adding a corrective blue layer for the indoor lights.
      Then using the a mask on this layer to hide where the correction isn't
      needed.
      Then I'll do the same for the blue-bleed from outside lighting.
      This also works if there is some weird flourecent lights too.
      Sometimes a finished pano as a .PSD file will as many as 5-6 color
      adjustment layers in tough situations.
      There may only be a small bit of each adjustment layer revealed through its
      mask though.
      Here's a screen shot of the layers pallet on a finished touch-up:
      www.photosurveyor.com/tutorials/layers.jpg
      I learned this from someone on this forum a long time ago.
      Wish I could remember who.
      Thanks to that person is due.

      Shawn





      ----- Original Message -----
      From: "Nelson Mendes" <nmendes@...>
      To: "panotoolsng" <panotoolsng@yahoogroups.com>
      Sent: Thursday, February 28, 2008 4:39 AM
      Subject: [PanoToolsNG] Fwd: White Balance in Panoramas


      > 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.
      > My workflow is something like this:
      >
      > I shot 6 + 1 Zenith Shots in 6MP Raw files for each panorama with the same
      > white balance setting (not using AUTO, usually I use the shadow setting on
      > Nikon).
      > I process those Raw files inside Photoshop to extract a final JPG of each
      > one.
      > I stitch them in PTGui
      >
      > And that's about it... (well, usually I shot a couple of photos more, to
      > cope with exterior light that usually burns the windows and mask those
      > over
      > the final panorama file).
      >
      > The problem is that usually I have incandescent light inside and sun light
      > on the outside, and that creates bluish tones (or redish tones depending
      > on
      > the white balance setting) on some areas of the panorama (like in open
      > doors
      > that lead to rooms with a great amount of outside light).
      >
      > What's is your best strategy to deal with this? I know that I can generate
      > from the Raw files, jpgs with different white balance settings and one
      > solution could be mask those in photoshop, but that's so time consuming
      > and
      > so prone to errors that it's not an option for me at this moment.
      >
      > Thanx.
      >
      > Nelson Mendes
      >
      >
      > [Non-text portions of this message have been removed]
      >
      >
    • Sacha Griffin
      You can create rgb channel masks, using an alternative white balance for the highlights. It s only a 5 second process and works great. ... -- Sacha Griffin
      Message 2 of 23 , Feb 28, 2008
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        You can create rgb channel masks, using an alternative white balance for the
        highlights.
        It's only a 5 second process and works great.


        On 2/28/08, Shawn Steigner <owner@...> wrote:
        >
        > I use a color(or level) adjustment layer in Photoshop.
        > Adding a corrective blue layer for the indoor lights.
        > Then using the a mask on this layer to hide where the correction isn't
        > needed.
        > Then I'll do the same for the blue-bleed from outside lighting.
        > This also works if there is some weird flourecent lights too.
        > Sometimes a finished pano as a .PSD file will as many as 5-6 color
        > adjustment layers in tough situations.
        > There may only be a small bit of each adjustment layer revealed through
        > its
        > mask though.
        > Here's a screen shot of the layers pallet on a finished touch-up:
        > www.photosurveyor.com/tutorials/layers.jpg
        > I learned this from someone on this forum a long time ago.
        > Wish I could remember who.
        > Thanks to that person is due.
        >
        > Shawn
        >
        > ----- Original Message -----
        > From: "Nelson Mendes" <nmendes@... <nmendes%40artlayer.com>>
        > To: "panotoolsng" <panotoolsng@yahoogroups.com<panotoolsng%40yahoogroups.com>
        > >
        > Sent: Thursday, February 28, 2008 4:39 AM
        > Subject: [PanoToolsNG] Fwd: White Balance in Panoramas
        >
        > > 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.
        > > My workflow is something like this:
        > >
        > > I shot 6 + 1 Zenith Shots in 6MP Raw files for each panorama with the
        > same
        > > white balance setting (not using AUTO, usually I use the shadow setting
        > on
        > > Nikon).
        > > I process those Raw files inside Photoshop to extract a final JPG of
        > each
        > > one.
        > > I stitch them in PTGui
        > >
        > > And that's about it... (well, usually I shot a couple of photos more, to
        > > cope with exterior light that usually burns the windows and mask those
        > > over
        > > the final panorama file).
        > >
        > > The problem is that usually I have incandescent light inside and sun
        > light
        > > on the outside, and that creates bluish tones (or redish tones depending
        >
        > > on
        > > the white balance setting) on some areas of the panorama (like in open
        > > doors
        > > that lead to rooms with a great amount of outside light).
        > >
        > > What's is your best strategy to deal with this? I know that I can
        > generate
        > > from the Raw files, jpgs with different white balance settings and one
        > > solution could be mask those in photoshop, but that's so time consuming
        > > and
        > > so prone to errors that it's not an option for me at this moment.
        > >
        > > Thanx.
        > >
        > > Nelson Mendes
        > >
        > >
        > > [Non-text portions of this message have been removed]
        > >
        > >
        >
        >
        >



        --

        Sacha Griffin
        Southern Digital Solutions LLC
        http://www.southern-digital.com
        http://www.seeit360.net
        404-551-4275


        [Non-text portions of this message have been removed]
      • Nelson Mendes
        Shawn, that s what I call time consuming task. It s more or less the way I m doing the corrections (I use Photo Filter Adjustment layers in CS3 and mask the
        Message 3 of 23 , Feb 28, 2008
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          Shawn, that's what I call "time consuming" task. It's more or less the
          way I'm doing the corrections (I use Photo Filter Adjustment layers in
          CS3 and mask the parts I don't need) but the masks sometimes are hard
          to do without using transparency gradients or the edges will show up
          on some areas where the WB is correct. I was wondering if anyone had a
          different (magic??) approach to this :)

          --- In PanoToolsNG@yahoogroups.com, "Shawn Steigner" <owner@...> wrote:
          >
          > I use a color(or level) adjustment layer in Photoshop.
          > Adding a corrective blue layer for the indoor lights.
          > Then using the a mask on this layer to hide where the correction isn't
          > needed.
          > Then I'll do the same for the blue-bleed from outside lighting.
          > This also works if there is some weird flourecent lights too.
          > Sometimes a finished pano as a .PSD file will as many as 5-6 color
          > adjustment layers in tough situations.
          > There may only be a small bit of each adjustment layer revealed
          through its
          > mask though.
          > Here's a screen shot of the layers pallet on a finished touch-up:
          > www.photosurveyor.com/tutorials/layers.jpg
          > I learned this from someone on this forum a long time ago.
          > Wish I could remember who.
          > Thanks to that person is due.
          >
          > Shawn
        • Nelson Mendes
          Sasha, can you explain me better that process? is there a link or a picture I can see? The 5 seconds words got my attention ;) ... for the
          Message 4 of 23 , Feb 28, 2008
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            Sasha, can you explain me better that process? is there a link or a
            picture I can see? The "5 seconds" words got my attention ;)


            --- In PanoToolsNG@yahoogroups.com, "Sacha Griffin" <sachagriffin@...>
            wrote:
            >
            > You can create rgb channel masks, using an alternative white balance
            for the
            > highlights.
            > It's only a 5 second process and works great.
            >
            >
          • luc.villeneuve
            I import my images in Aperture color balance ONE image with the very efficient tools in Aperture then copy the settings from this image and paste the settings
            Message 5 of 23 , Feb 28, 2008
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              I import my images in Aperture color balance ONE image with the very efficient tools in
              Aperture then copy the settings from this image and paste the settings to the other images.

              Time consuming is a relative concept.
            • Georgia Real Tours
              ... Hi Nelson, I m not sure exactly how to mix white balances under different lighting conditions, but I do have a suggestion that might lead to something
              Message 6 of 23 , Feb 28, 2008
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                On 2/28/08, 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.
                > The problem is that usually I have incandescent light inside and sun light
                > on the outside, and that creates bluish tones (or redish tones depending on
                > the white balance setting) on some areas of the panorama (like in open doors
                > that lead to rooms with a great amount of outside light).

                Hi Nelson,

                I'm not sure exactly how to "mix" white balances under different
                lighting conditions, but I do have a suggestion that might lead to
                something useful. I just got a WhiBal set, and haven't yet had an
                opportunity to test it out well enough. However, my idea was to
                choose a single light source to do the rest of the pano's white
                balance. In your case with a WhiBal, here's what I'd do: I'd shoot
                the WhiBal under each light source. I'd then create a series of RAW
                files optimized for each white balance. Once I did that, I'd create a
                pano (strips, cubes, equi, etc.) for each optimized white balance.
                After that, there's several different methods of combining them.

                All of that may sound like a lot of time-consuming work, but I don't
                think it would be. You'd simply be shooting an extra shot for each
                light source and making an equivalent number of RAW sets as are
                light-source shots. And if you are using Bibble, you don't even have
                to do that. Additionally, once you have the required CPs for one pano
                you can batch stitch the rest.

                If you don't know what I WhiBal is (and I don't expect you to, I just
                found out about it not long ago) it is a neutral color board whose
                color value is known. You can find out more about it at
                http://www.rawworkflow.com/products/whibal/index.html
                <http://www.rawworkflow.com/products/whibal/index.html> While I
                haven't yet tried it in a pano, it certainly has helped with regular
                photos!

                Cheers,
                Robert~
                --
                Mid GA: 478-599-1300
                ATL: 678-438-6955
                garealtours.com
              • Eric O'Brien
                I have been including a neutral gray ( grey ) target every time I shoot a panorama, for quite a while. Certainly in many artificial (architectural)
                Message 7 of 23 , Feb 28, 2008
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                  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.)

                  Aside: I consider it unfortunate that the term apparently has
                  settled at "White Balance," when in fact it has to do with NEUTRAL
                  balance. You might want to read
                  Gray or White Card for Neutral Balancing?

                  <http://rmimaging.com/information/gray_or_white.html>

                  "Although the camera calls it 'white balance,' most cameras do not
                  actually use a white card to perform this operation. Instead, they
                  use a gray card, or a white card exposed so it appears gray. More
                  properly white balance should be called neutral balance or, even
                  better, light balance. What is actually happening is the balance
                  between the color channels in the camera (red, green and blue,
                  usually) are adjusted so a gray item will be imaged with equal RGB
                  values under a given lighting."


                  For my "neutral balance target" I currently use (yes) a WhiBal
                  card. ;) Another nice one is the Digital Gray Card from Robin Myers
                  Imaging <http://secure.netsolhost.com/664583.677720/Merchant2/
                  merchant.mvc?Screen=CTGY&Store_Code=CI&Category_Code=GC>. Any
                  "Photographic Grey Card" should work pretty well too.


                  Addressing the original question, here's the way I currently work:

                  I shoot in Raw. Although when using raw, the color temperature
                  setting is not relevant, I still tend to set it to something that is
                  close to what I consider the dominate lighting in my scene. (This
                  just makes things easier when reviewing the images later.) I
                  *always* include a neutral target in my first shot (the "slate"
                  shot). [Yes, this means that my "4 shot" panorama actually requires
                  FIVE shots; my 9 shot panorama requires 10 shots, etc.]


                  Comment on Digital vs. Film: it seems to me that color difference
                  between light sources are much less extreme using digital capture
                  than when using film. Daylight compared to Tungsten is far less
                  "electric blue"; Incandescent lamps are far less "candle-flame-red"
                  when compared to daylight; Florescent lamps are not nearly so
                  hideously green.


                  I assume that even naive viewers implicitly realize that tungsten
                  light tends to be redder, "North sky light" tends to be bluer [for
                  those in the Southern Hemisphere, that would be "South sky light."
                  Or perhaps we should say "Polar Direction Influenced Light. :) ]

                  So... I tend to balance the color temperature of each pano toward
                  what I consider the "dominant light" of the scene. A room lit by
                  interior tungsten lights, having a "anti sun" window? Turn the dial
                  until the window looks very blue and the interior only slightly red.

                  Based on my believe the people (viewers) inherently understand that
                  exterior light is likely to be bluer than interior light and that
                  interior light is likely to be redder than exterior light, I just
                  "turn the dial" until I feel the mixture is a plausible balance
                  between interior and exterior light.

                  I do NOT try to "neutralize" colors across all light sources. I feel
                  that would look strange and feel unnatural. That is, "we know" that
                  interior light is reddish. If you set the color balance of an
                  interior light scene to dead neutral, it will look strange.


                  By the way: a fabulous trick, apparently not well known: In
                  Photoshop, open ANY file as if it were a Camera Raw file. This
                  gives you access to all the Camera Raw controls, which *include*
                  those nifty "Temperature" and "Tint" sliders.

                  In Photoshop, choose File > Open... Navigate to the file you want
                  to open. Select it (click on the name ONCE). Change the "Format:"
                  pop-up to "Camera Raw" [NOT "Photoshop Raw... that's a totally
                  different thing] and proceed.

                  eo

                  On Feb 28, 2008, at 7:38 PM, Georgia Real Tours wrote:

                  > On 2/28/08, 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.
                  >> The problem is that usually I have incandescent light inside and
                  >> sun light
                  >> on the outside, and that creates bluish tones (or redish tones
                  >> depending on
                  >> the white balance setting) on some areas of the panorama (like in
                  >> open doors
                  >> that lead to rooms with a great amount of outside light).
                  >
                  > Hi Nelson,
                  >
                  > I'm not sure exactly how to "mix" white balances under different
                  > lighting conditions, but I do have a suggestion that might lead to
                  > something useful. I just got a WhiBal set, and haven't yet had an
                  > opportunity to test it out well enough. However, my idea was to
                  > choose a single light source to do the rest of the pano's white
                  > balance. In your case with a WhiBal, here's what I'd do: I'd shoot
                  > the WhiBal under each light source. I'd then create a series of RAW
                  > files optimized for each white balance. Once I did that, I'd create a
                  > pano (strips, cubes, equi, etc.) for each optimized white balance.
                  > After that, there's several different methods of combining them.
                  >
                  > All of that may sound like a lot of time-consuming work, but I don't
                  > think it would be. You'd simply be shooting an extra shot for each
                  > light source and making an equivalent number of RAW sets as are
                  > light-source shots. And if you are using Bibble, you don't even have
                  > to do that. Additionally, once you have the required CPs for one pano
                  > you can batch stitch the rest.
                  >
                  > If you don't know what I WhiBal is (and I don't expect you to, I just
                  > found out about it not long ago) it is a neutral color board whose
                  > color value is known. You can find out more about it at
                  > http://www.rawworkflow.com/products/whibal/index.html
                  > <http://www.rawworkflow.com/products/whibal/index.html> While I
                  > haven't yet tried it in a pano, it certainly has helped with regular
                  > photos!
                  >
                  > Cheers,
                  > Robert~
                  > --
                  > Mid GA: 478-599-1300
                  > ATL: 678-438-6955
                  > garealtours.com
                  >
                • Rodolpho Pajuaba
                  Instead of using RGB masks, the real solution is to look at the a and b channels after converting a copy to Lab. If the problem is in the yellow blue axis,
                  Message 8 of 23 , Feb 29, 2008
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                    Instead of using RGB masks, the real solution is to look at the "a" and
                    "b" channels after converting a copy to Lab. If the problem is in the
                    yellow>blue axis, you´ll very likely be able to build a very accurate
                    mask from the "b" channel, and apply it to a top, differently-corrected,
                    layer. Not magic, it´s just a matter of knowing the available tools.
                    Regards,
                    Rodolpho Pajuaba

                    Nelson Mendes escreveu:
                    > Shawn, that's what I call "time consuming" task. It's more or less the
                    > way I'm doing the corrections (I use Photo Filter Adjustment layers in
                    > CS3 and mask the parts I don't need) but the masks sometimes are hard
                    > to do without using transparency gradients or the edges will show up
                    > on some areas where the WB is correct. I was wondering if anyone had a
                    > different (magic??) approach to this :)
                    >
                    >


                    [Non-text portions of this message have been removed]
                  • Georgia Real Tours
                    ... Wow, Eric! One of the most helpful and informative posts I ve read on this subject. :c) Cut-and-paste ready for the wiki, afaik. BTW, you re method of
                    Message 9 of 23 , Feb 29, 2008
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                      On 2/29/08, Eric O'Brien <ericob@...> wrote:
                      >
                      > I have been including a neutral "gray"("grey") target every time I
                      > shoot a panorama, for quite a while...

                      Wow, Eric! One of the most helpful and informative posts I've read on
                      this subject. :c) Cut-and-paste ready for the wiki, afaik.

                      BTW, you're method of one extra shot in the pano with the neutral card
                      is what I was envisioning. Nice to see I was headed down a working
                      path. ;c)

                      Thanks!

                      Robert~

                      --
                      Mid GA: 478-599-1300
                      ATL: 678-438-6955
                      garealtours.com
                    • 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 10 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 11 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 12 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 13 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 14 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 15 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 16 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 17 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 18 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 19 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 20 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 21 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 22 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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