Dan Scott said:
>
> Hey! I think I actually understood that explanation.
It would have been even better if I'd said what I meant, namely:
" . . . This means that there are several surface materials that
> all appear to have the same colour when viewed by one type of sensor
> under different light source, but which can have wildly different
> colours when viewed by another type of sensor"
>
> Is this what I keep seeing referred to as 'metamerism'
Yes - that's one example of metamerism, or colour space aliasing.
> John Francis wrote:
>
> >Actually it's a great deal more complicated than that. The human
> >eye, like colour film, is a tristimulus response system - it assigns
> >a colour to an object based on the total intensity of light measured
> >by three different sensors, each of which has a response curve that
> >is more or less sensitive to different frequencies in the spectrum.
> >
> >Any coloured object, furthermore, reflects some amount of light that
> >falls on it - more light in the areas of the spectrum that correspond
> >to the perceived colour of the object; less in other parts. So the
> >total excitation of the colour sensors is the product ('convolution',
> >for the mathematically inclined) of the frequency spectrum of the
> >light source, the reflection curve of the surface, and the response
> >curve of the sensor. All this boils down to one intensity level.
> >Obviously there are many combinations of spectrum and refelction
> >that will yield the same intensity when measured by a particular
> >sensor. This means that there are several surface materials that
> >all appear to have the same colour when viewed by one type of sensor
> >under different light source, but which can have wildly different
> >colours when viewed under a light source with a different spectrum.
> >
>
>
>
>
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