[argyllcms] Re: Best way to proceed?


On Sunday 01 June 2008 12:17:11 Ben Goren wrote:
> On 2008 Jun 1, at 11:24 AM, Hal V. Engel wrote:
> > On Saturday 31 May 2008 15:53:29 Ben Goren wrote:
> > > To make matters worse, some of the woods are very slightly
> >
> > iridescent,
> >
> > > and change luminance (mostly) and hue (slightly) rather noticeably
> > > with shifting lighting angles....
> >
> > I don't think this is iridescence but rather it is the
> > characteristics of the wood grain which is a 3D structrure [. . . .]
>
> Whatever the physics behind it -- and your description certainly makes
> sense -- it's a /huge/ part of the problem here. Indeed, some of the
> pieces use exactly the kind of maple you used as an example.
>
> I just finished shooting some example pictures. The scene is
> identical. The first shot is with only the left light on; the second,
> both lights; and the third, only the right. Both lights are at a 45o
> angle, both to the side and above. I've made no attempts at
> correction; these are Camera Raw's defaults with the white balance
> taken from a grey card.

I guess the main point I was trying to make was that this specific issue is 
not a colorimeteric issue.  Rather it is a lighting issue related to how that 
lighting interacts with the subject.  Your three test photos clearly show how 
this interaction works.  As such it is more about the ART of photography and I 
don't think there is any science that can be applied that will just "fix" it 
so that you can do exactly the same thing with each piece.  

Each of these pieces will respond to the light in different ways because that 
is the nature of the materials in the subject and the lighting that optimally 
brings out the grain and figure of one piece can be far from optimal for the 
next one.   In fact in your sample shots it appears that even in the same 
piece that different parts of the piece need different lightling to get 
optimal results.  Because of that you will need to either decide that you can 
ignore this aspect or that each subject needs to have different lighting to be 
shown it to it's best.  This will be a challenge but it appears to me that you 
are up to learning about this and perhaps will come up with some systematic 
process that allows you to get near optimal results without too much effort.  
I wish I could be of more help but at least you now have an idea what it is 
you are dealing with and that is the first step in solving any problem.

Hal

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