[Leica] On camera gamuts and the M8

[davison_m at msn.com (MARK DAVISON)]

Brian,

The additivity with respect to wavelength is absolutely a fundamental part 
of the standard models used in color science, both for modelling digital 
cameras and the color matching behavior of the human visual system. I'm not 
a physicist, so I can't verify if the model is reasonable.

Physical studies of neural response of verterbrate vision systems are more 
complicated, but I've just started to read about that.

Mark



>From: Brian Reid <reid@mejac.palo-alto.ca.us>
>Reply-To: Leica Users Group <lug@leica-users.org>
>To: Leica Users Group <lug@leica-users.org>
>Subject: Re: [Leica] On camera gamuts and the M8
>Date: Wed, 15 Nov 2006 19:51:00 -0800
>
>Mark,
>
>Thanks for taking the time to write that. It's illuminating.
>
>I have a question.  In the sentences following this:
>
>>You could determine the camera gamut via the following experiment:
>>  take a tunable source of monochromatic light....
>
>aren't you making the assumption that the camera sensor hardware is 
>distributive? For example, aren't you assuming that (within clipping 
>limits) the Red sensor output to monochromatic light colors a and b 
>satisfies
>        R(a+b) = R(a)+R(b) ?
>
>I have no idea if sensors actually behave this way or not, but given that 
>they are made out of physical materials, I have a sense that R(a+b) is 
>probably not equal to R(a)+R(b).
>
>I would also fear that
>        (R(a)+R(b))/(G(a)+G(b))
>is not equal to
>        R(a+b)/G(a+b)
>in other words, that there is a color shift in the response to one color 
>when you add another color to the mix. I guess I would call this property 
>linearity.
>
>If sensors really do get both of those right, then the world is a kinder 
>gentler place than I am used to. And if they do not, then I'm not even sure 
>I know what "device gamut" means, other than being a theoretical bound on 
>the output of the sensor.
>
>Brian Reid
>
>
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