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Tag: color

Yellow flower VS Special White light

Video by Benoit Dusart, 2017

3rd of 3 projects at été 78

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été78 p3

Hommage à Edwin H. Land, 2017

Halogen lamps, special white lamp designed in collaboration with GVA lighting (model FL-100), various objects

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The space is illuminated by two different white lights that have the same whiteness and color temperature (about 3000K). Common colorful objects are displayed on two pedestals: fruits, flowers, color samples, beer bottles, etc.

The objects illuminated by the special white light dramatically change: pilsener beer look like sparkling rosé, dull blue objects appear bright turquoise, warm yellow plastic becomes bright orange, lemons become whitish, dark purple flowers appear dullish blue.

All colors except for white, grey and black are changing. People with “normal” color vision are experiencing something like color-blindness. People’s skin and blue eyes also change, they somehow appear more beautiful…

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Here’s the text written for the show (in French):

Opening, 2nd of 3 projets @ été78

There’s still a chance to see this 2nd chapter of the exhibition on Saturday March 11 at été78, rue de l’été 78, 1050 Brussels.

Exhibition views, été78, 1st of “3 projets”

Diaporama

Views from the 1st part of the exhibition “Mémoire d’atelier sur trois projets” at été78 in Brussels. The text draft is available here: Soleil de minuit text

Contrast

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2PM

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1PM – sun starts illuminating the background

 

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Rosace, quasicristal dodécagonal

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Variations of the visual appearance of a stained glass window during the course of the sun in the sky.

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Le ciel, le soleil et un vitrail orienté Est

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[Document in French] A timeline of the visual appreance of a stained-glass, in parallel the colors of the Sunlight and the colors of the Sky, during a sunny summer day.

(PC : click-droit > “ouvrir l’image dans un nouvel onglet” pour voir l’image en grand)

(right-click > “open image in a new tab” to zoom)

Sunlight / Stained-glass

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Simulation of the changing visual appearance of an East-oriented Stained-glass window depending on the daylight color and orientation:

7:30 AM: before the sun rises, the sky illuminates the window

7:45 AM: a yellow Sunlight reaches the window

8:00 AM: the Sunlight is already whiter

12:00 AM: the Sunlight is white

12:30 AM: the Sunlight disappears, only the sky illuminates the window

4:00 PM: idem

6:00 & 8:00 PM: the sky’s color changes slightly

All this has been simulated using physical data about the light of the Sun and the Sky in the south of France, and physical data acquired by scanning colored glass with a spectrophotometer.

 

Glass-light interactions on the prototype

window-detail

With the studio Debongnie (http://vitraux-debongnie.be), we are working on a Stained-Glass prototype to be installed in a 13th Century Cistercian Abbey in the south of France. My project passed the pre-selection and we are in the final of the competition against 2 other duos artist/glass-studio.

Cistercians didn’t put colors, pictures or crosses on their windows. Their windows were supposedly « albae fiant, et sine crucibus et pricturis » (white – or colorless(?) -, and without cross and representations). Very few original 12 & 13th Century Cistercian windows survived and we know little about how they interpreted this rule.

My proposal is to produce “white light” in the Abbey, by a combination of different optical types and colors: transparent light greenish blue, light blue and light reddish blue mostly, and opalescent whites that diffuse light and are less transparent.

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METAMORPHOSIS

During the course of a sunny day, the light will vary. The visual appearance of the window will be changing a lot because of this variation.

Behind the window is a yellowish-white stone-wall. Before noon the window and the wall behind it are in the shadow. Around noon, the sun illuminates the window directly and the opal glass are becoming very bright. During the afternoon the wall behind becomes illuminated, allowing the transparent colors to appear. Finally around 4-5PM the shadow moves on the window and the opal glass stops being so bright.

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GOLD + BLUE = WHITE LIGHT

Interestingly, opal glass will appear white but will project amber light on the walls or the floor of the building. The average color of the light passing through the window has been computed to be white. The glass selected last month in the factory Lamberts in Waldsassen were chosen to produce this effect, and the situation has been simulated with the light spectrum as measured last summer in the south of France.

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BLUE SKY REVEALS THE COLORS

Finally, there’s the possibility of seeing the sky from an angle in the Abbey. When people will look at the window with the sky behind, it will reveal new colors again. What looked almost colorless will appear as different shades of blue and yellowish whites.

 

Picture of the first third of the window-prototype

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Finally, the glass version !

This is a stained glass element made with a traditional technique. The black lines are a combination of hand painted “grisaille” and lead.

I’ll soon describe the entire project in a longer post, stay tuned ;)

 

…working on a Stained-Glass prototype

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A paper model with “scanned” and calculated colors for the blue sky behind…

Below, the left one simulates a cloudy sky, the right one the blue sky

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This is the design made by something like 5000 lines of code in Python 2.7 ;)

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Serious glass sheet optical anatomy

g161

The first result of the algorithm

1im

A

1back

B

glass-spectrums

C

A & B & C : the raw material, pictures and glass transmission spectra (blue for different densities of the sheet, black for a reference white glass of the same factory)

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In the previous post I showed some pictures produced by my technique of background removal for making “as accurate as possible” photos of glass sheets.

The photos were taken on a TL back-lighted, which is highly irregular. What you have to do is basically to multiply the picture A by the inverse of the picture B, after calibrating the pictures A & B together by making sure that their background has the same lightness. Of course you should do this in RAW linear 16bit!

This simple operation removes: the optical artefacts (the lens of the camera filters more light in the picture’s borders) the electronic ones (the CCD is slightly non-linear). It also automatically generates a “perfect” white balance, whatever your light source is… The only pity is that it adds some noise, but for our application this is fine.

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I developed a method for selecting parts of the glass sheets based on their spectral transmission, by combining spectrophotometric measurements, math, and the corrected pictures :

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The 3 zones A, B, C have an average difference of 14% in luminance when Blue-sky light passes through them.

other glass sheets characterized in the same way:

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Photographic Glass Characterization

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Graded Cobalt Blue light ref. G161, origin: Glasshütte Lamberts (Germany)

rose_or_clair

Graded Gold Pink pieces, origin: Glasshütte Lamberts (Germany)

uv

Non-standard yellow ref. Special Yellow UV sample, origin: Glasshütte Lamberts (Germany)

1242xx_2332

Light Turquoise ref. 1242xx, origin: Glasshütte Lamberts (Germany)

1302f_3034

Dull and relatively light Blue-Violet, ref. 1302F, origin: Glasshütte Lamberts (Germany)

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When working with mouth-blown “Antique” glass (the glass traditionally used to make stained-glass), the irregularity of the material is a given property. Every sheet is unique and its thickness varies between 2 to 6-7 mm, with an average thickness of about 3 mm.

For perfectly transparent sheets, the color of the glass depends on the thickness of the material. If you want to have a high-level of control over the color that you want, a possibility is to measure the glass thickness using a digital camera and a light table.

However, this is not easy. The light-table non-uniformity has to be taken into account to correct the pictures, as I did here.

It’s been a few months that I’ve been developing software/hardware solutions to perfeclty measure the transmission of light that is characteristic of every single piece of mouth-blown glass. It now works pretty well.

(If ever you are interested by the technique you can leave a msg!)

 

 

Opal glass collection

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I spent this week in the glass studio Peters Glasmalerei in Paderborn (Germany) and came back with a few opal-plated mouth-blown antique glass samples.

See: http://www.peters-studios.com

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