PanoTools mailing list archive

Mailinglist:PanoTools NG
Sender:William Donelson
Date/Time: 5-Mar-2008 02:21:35 +0100
Subject:Re: White (Neutral) Balance in Panoramas

Thread:


--- In #removed#, 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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