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## Tag: gris

### D65 n°3, transparences / lampe / spectres, 2012

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Below, detail: desaturated daylight spectrum

### a new step: color with colors

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Average colors of the Blackbody radiation colors (from 3500°K to 9500°K) and the color of the background. 50% of the paper is covered by paint. (This actually equals a desaturated picture of these colors, i.e. the mixture of blackbody colors and white D65 light at equal power)

Doing optical greys with colors might become history in my work, I start doing colors with colors – let me say something about my color system here:

I use colors following “Grassmann laws,” that means that I measure the lights coming from my pigments to your eyes, and by varying the proportions of these pigments I change the average color of the light that comes to you.

That works exactly in the same way as you computer’s screen except that I have more primary colors and usually less light.

Here, I used 7 “primaries”: Ultramarine Blue greenish extra, Cobalt Turkish light, a Green mixture of the former and of the next, Cadmium Yellow light, Cadmium Red “Cinnaber” shade and Titanium White (see below)

The “primaries” of my system (didn’t use the Cobalt Pink here yet!)

To create a color, I will make the average of 4 of these primaries, so a “possible” color will always be located in a “pyramidal space” with a primary color at each peak.

If I add the Black  primary, the main pyramids will be:

ReGrBlu-White and ReGrBlu-Black. Around them you’ll have ReGrYe-Whi/Bk ;  GrBluTu-W/Bk ;  ReBluPink-W/Bk

Which makes a total of 8 pyramids that touch each other and define the gamut of my system! (see below)

8 pyramids = gamut of 8 colors

The best solution to get the amounts a, b, c, d of the colors A,B,C,D  required to get a given color M is to use matrix calculus:

with: a+b+c+d=1,

$\vec{M} = a.\vec{A} + b.\vec{B} + c.\vec{C} + d.\vec{D}$

the colors coordinates are in the CIE 1931 XYZ color space, so we create a square matrix with the color coordinates for each color, multiply by the solution, and equal it with the color we want:

$\begin{pmatrix} M_x \\ M_y \\ M_z \\ 1 \end{pmatrix} =
\begin{pmatrix} A_x & B_x & C_x & D_x \\ A_y & B_y & C_y & D_y \\ A_z & B_z & C_z & D_z \\ 1 & 1 & 1 & 1\end{pmatrix}
\times \begin{pmatrix} a \\ b \\ c \\ d \end{pmatrix}$

Then we solve this:

$\begin{pmatrix} a \\ b \\ c \\ d \end{pmatrix} = P \times \begin{pmatrix} M_x \\ M_y \\ M_z \\ 1 \end{pmatrix}$

with P being the inversion of our matrix:

$P = \begin{pmatrix} A_x & B_x & C_x & D_x \\ A_y & B_y & C_y & D_y \\ A_z & B_z & C_z & D_z \\ 1 & 1 & 1 & 1\end{pmatrix}^{-1}$

That’s it!

Thank you very much PA5CAL from this forum to have helped out!

http://forums.futura-sciences.com/physique/555235-aide-cherche-equation-proportions-de-couleurs-moyennees.html

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Today could be a great day for painting: Georges Seurat’s dream-project of a “scientific painting” advanced a little. I’m sure he would be (very) happy to see this. I wish I had the email of the painter’s paradise, I would send this to him and all his friends…

### D65 n°3 part II starts

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I’m gonna do a “lamp simulation” (a circular gradient with constant tint and varying brightness, based on the abstract model of a “perfect lamp,”) based on 11 colors: 3 times RGB with 3 levels of brightness (I dont enter into the detail of how I choosed them) and Black/White.

### hi-resolution pictures of the prototype

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Light ON/OFF, hi-resolution orthographic panorama made with Hugin.

For me, there’s not much difference between such a work (the prototype, made of laserprints on paper) and a “traditionnal painting.”

I’m really starting to think it’s just the same thing, like Richter includes amateur photography in the field of “painting.”

The central part being equalized.

Something is slightly wrong – the values are increasing where the light is intense -, but it’s still very close to what I wanted (an equalized luminance everywhere in the rectangle).

### good & bad news :)

The bad news: the laser printer cannot handle large black prints, some unit of the printer makes a random glossy layer on it.

the random gloss

the (very) good news id that the luminance correction is not very angle-dependant, means that except for that random gloss, the correction works at a wide variety of viewpoints, that’s really nice.

from the left side, the gloss dissappears and the flat is still “flat.”

below: zooms on different parts from the left side (same shutter speed)

### calibration, 1st measures, samples

The calibration of the material is a heavy task – but now the system works.

Below are two pictures representing light measurements in RAW mode (linear) on my digital camera, every pixel is made after 1 photo which has been croped and averaged, and they correspond to +- 10 x 10 cm zones of the wall.

The 1st picture has been made with 1/4 sec. aperture, the second with 1/2 sec.

The continuitiy has been reproduced after the pixel values in a spreadsheet program (see below).

It looks pretty surprising, but the Black density of the random-pixel-distribution printed samples placed on the wall corresponds exactly to the correction needed to make a “ganzfeld.”

That means that: THE AMOUNT OF DIFFUSED LIGHT IS STRICTLY EQUAL (well… sctrictly is a big word! :) AT POSITION A, B, C etc.

However, the eye & brains “fight” against these equalities, trying to “tell” that the sample A is darker and B is lighter, even if the amount of light that they redirect in my direction is strictly equal for A & B

### wall to be visually uniformized: “ganzfeld” prototype

I will try to create a “ganzfeld” on this wall by subtracting light (using black printed patterns.)

This is the object of my residency at Netwerk, Aalst, BE, from last Monday to next Saturday.

More documents will come…

### D65 lighting prototype @ JVE, Maastricht – 2011

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D65 Normlicht light tubes mounted with an aluminium reflector

”Table-Tops Room,” Jan van Eyck Academie, Maastricht, NL, 2011

### D65 #3 1st “fake lamp”

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Thanks to a brief moment of sunlight here I could make a very clear picture.

I will be where they did this for 3 weeks ;)

### fake Light, 1st TW pass (in progress…)

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The lightness will change as if there was a perfect lamp at 17 cm from the center of the figure.

The white structure appears really “transparent.”

This geometrical solution could be called the “pixel solution,” since the surface is divided in 2×2 cm squares, other solutions are possible and will be tried later on the study: concentric zones, gradients… The only color added to the grey background is Titanium White (TW), later I’ll try color, enjoy ;)

### transparent square

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Fine-tuning of titanium-White and carbon-Black to “match’ the lightness of the grey background. Bizarre: following my measurements it was supposed to disappear in the middle, maybe a mistake…

detail below, click to zoom!

### (will) disappear

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Fine-tuning of titanium-White and carbon-Black to “match’ the lightness of the grey background.