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Re: [PanoToolsNG] Fwd: White Balance in Panoramas

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  • 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 1 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 2 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 3 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 4 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 5 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 6 of 23 , Mar 1 5:33 AM
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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 7 of 23 , Mar 1 6:39 AM
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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 8 of 23 , Mar 4 6:53 AM
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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 9 of 23 , Mar 4 9:04 AM
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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 10 of 23 , Mar 4 5:21 PM
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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 11 of 23 , Mar 4 11:28 PM
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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 12 of 23 , Mar 7 6:30 AM
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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 13 of 23 , Mar 8 7:33 PM
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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 14 of 23 , Mar 8 9:24 PM
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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 15 of 23 , Mar 8 10:07 PM
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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 16 of 23 , Mar 10 12:14 PM
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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 17 of 23 , Mar 10 2:51 PM
                                    • 0 Attachment
                                      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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