Re: Color Mixing (Pigment) question

[Bernard Cleyet <anngeorg@PACBELL.NET>]

interleaved

John Denker wrote:

> Bernard Cleyet wrote:
>
>
> > this is the argument of the pointillists and impressionists.  [pure
> > colour splotches instead of mixing on the pallet mixed by the eye, a
> > more brilliant result]
>
> More brilliant than what?
>
> An arrangement of pure green paint splotches intermixed
intermixed?  the splotches are side by side.

> with pure blue paint splotches cannot possibly be more
> brilliant than covering the same area with an ordinary
> bright cyan paint.  OTBE (other things being equal) you
> would expect it to be roughly half as bright.
>
> Think about the physics:  There is roughly a 50% chance
> that a given incident blue photon will land on a green
> splotch and be absorbed.  Similarly there is roughly a
> 50% chance that a given incident green photon will land
> on a blue splotch and be absorbed.  A solid area of
> ordinary bright cyan
depends on how the cyan paint is created.

> paint will be much less likely to
> absorb either one of those photons.
>
> I'm simplifying things somewhat.  Smart-alecks can conjure
> up pathological counterexamples.  But what I'm saying is
> a good approximation under normal natural conditions.
of course there is the problem of covering varnishes, et cet. but the
"modern" painting always appeared brighter to me.  Maybe they used a lot
of brilliant white, but then the paint wouldn't look pure and instead
pastel.

The eye is not a photometer.

Color Theory

In its use of color, Impressionism dramatically broke away from
tradition. Advances in the fields of optics and color theory fascinated
these painters. Working outdoors, Impressionists rendered the play of
sunlight and the hues of nature with a palette of bolder, lighter colors
than classical studio painters used. In 1666, Sir Isaac Newton had shown
that white light could be split into many colors - including the three
primary colors, red, blue, and yellow by a prism. The Impressionists
learned how to create the prismatic colors with a palette of pure,
intense pigments and white. Unlike Academy painters, who covered their
canvases with a dark underpainting, Impressionists worked on unprimed
white canvas or a pale gray or cream background for a lighter, brighter
effect.

           Eugene Chevreul's 1839 book, On the Law of Simultaneous
Contrast of Colors, guided the Impressionist practice of laying down
strokes of pure, contrasting colors. Chevreul found that colors change
in relation to the other colors near them. Complementary colors, or
those directly opposite each other on his color wheel, create the most
intense effects when placed next to each other, he wrote. Red-green or
blue-orange combinations cause an actual vibration in the viewer's eye
so that color appears to leap off the canvas. No wonder viewers react
emotionally to the glittering sunlight on Monet's rivers or the splash
of orange costume on Degas' ballet dancers. "I want my red to sound like
a bell!" Renoir said. "If I don't manage it at first, I put in more red,
and also other colors, until I've got it."

So my argument maybe isn't correct, but the effect is real.

bc

>