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18436Re: White (Neutral) Balance in Panoramas

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  • William Donelson
    Mar 4, 2008
      --- 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.
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