Variations of the visual appearance of a stained glass window during the course of the sun in the sky.
[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)
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.
The glass-blowers at Glasshütte Lamberts (Waldsassen, Germany) are working every week-day between 4AM and 10AM, that’s a tradition, they said…
Last summer, I was on a trip to Waldsassen, Germany – next to the Czech Republic border – at the Glasshütte Lamberts factory. It is one of the few remaining factories in Europe where colored glass sheets for stained-glass are produced in a traditional way. Mouth-blown glass is made every week days by several teams of workers. First shaped as long bottles, the glass is recooked in a secondary step to be flattened into sheets of 0.54 m².
I went there to choose the colors that I want to use for the stained-glass project that I am working on. In the “standard” catalogue, Glasshütte Lamberts has a bit more than 250 references. But in the factory, there is much more: around 5000 different glass, the “non-standards”, which I came to see.
A part of the factory where 5000 different series of glass sheets are stored, every series being unique, and the office of color-expert and Sales Director Manfred Mislik, where we had a talk about colors.
Since I started to get in touvh with people in the stained-glass world several professionals asked me how I will choose the colors. I heard that working with glass is always a challenging experience and that for many artists, it was a difficult or even painful experience, either because there are too many possibilities, or because the appearance of the glass, its transparency, was too different from the logic of for example, painting.
When I got there I had a strategy: I came with a spectrophotometer and a light box that I built a few days before. In the office, I made 312 spectral measurements : all the standard catalogue, plus 75 “non-standard” colors that I picked up in the room, especially the very intense types: Plated deep Reds, Selenium Reds, Oranges, Yellows, and Gold-based Pinks.
One of the several trials at making gradients from deep Red to Yellow (imitating the Cadmium pigments series with Selenium glass)
Thanks to the spectral measurements I made, I could build a colorimetric database. I only had to get the spectrum of the LEDs that I will use in the installation to calculate the colorimetric coordinates of every single glass. It is necessary to have the spectrum of the light source that will illuminate the glass to be able to calculate the colors of the glass in a simulation, because these colors vary depending on the light that lights them up. I got the needed emission spectrum from the LEDs manufacturer :
The emission electromagnetic spectrum of the LEDs that I will use in the metro station to illuminate the stained-glass from behind.
All of this (the trip, the selection, the spectral measurements and the spectrum of the light source) were necessary pre-requisite steps to be able to start working.
The next steps will be discussed in a future post
A picture taken at sunset in San Marino last week, processed for display on the screen.
While this was obviously common sense for important painters such as Georges de La Tour, Rembrandt, and probably – I believe – for Georges Seurat, few people realize how twisted pictures – and today’s digital pictures – have to be in order to be displayed or printed by our imaging devices.
Serious people in the field of photography know about this too, of course, since this is their daily routine problem – however, they usually don’t care.
I am talking about the fact that when we experience real scenes in the real world, outside – like me when I took this picture in San Marino at sunset – the colours we see are very bright, intense, and the contrast within the different visible parts of the landscape is very high. Ruffly speaking, the contrast ratio between the lightest and darkest parts of the scene in the photo was between one and two hundred here, and the colours in the sky were much more vivid than what we see in the poor picture above.
When we use a digital camera, the data measured by the sensor is converted: it is mathematically flattened to fit the limits of a computer screen, for example.
But if we keep the original data (what photographers call the “RAW” picture), we actually have access to a much more accurate light measurement – even if it doesn’t “look good” on the screen, the value of each pixel is actually proportionnal to the amount of light in the original scene, plus the electronic noise of the camera’s sensor, plus the distortion of the lens, plus the irregularity of the sensor itself (usually a bit more efficient from left to right, or the opposite).
This is how the RAW image looks like on the screen:
Raw linear picture: pixel’s values are theoretically proportionnal to the amount of light in the original scene, but noise and optics interfere a bit.
When we print the picture, it’s even worse. While some colours will appear more intense than on the screen (cyan, yellow…) some others will fade, and the general contrast will drop. I have a quite good printer but still, the white of the media reflects 90.73% of the light that a pure white would reflect, and the pure black of the printer reflects 3.85% of it. That means the maximal contrast ration on a print is 23.56 – while for the original scene it’s between 100 and 200! It’s about 5 to 10 times less…
Now, what we can do and what nobody does, is to colorimetrically render – as exactly as possible – a fragment of the picture within the limits of what the printer can copy accurately. The amount of light will probably still be inferior to the one in the original scene, but the relations between the colours will be proportionnal to the ones in the original scene.
When we do this, we get as close as we can to making exact copies of (fragments of) the original scene. The better the camera sensor, the better the copy. What do we see? The colours are much closer from the original sunset. When we want the entire sky, we have to darken it, then the floor disappears more. Why? Because when we darken the sky more we ask the printer to print blacker than its black, which is impossible. Same if we want more floor: we ask the sky to become lighter than the media, which is unprintable…
La Tour understood this very well back in 1642… That’s why he hid the flame with the little girl’s hand. The fact is not a well-kept secret! :)
Georges de La Tour, Saint Joseph charpentier (detail), 1642, Musée du Louvre
Below are some examples of this, within the limits of my printer:
(Click on the pictures to zoom!)
Recently in the LIMA conference: http://lima-project.fr/programme-de-la-journee-industrielle-lima/ Noël Richard was tlaking about the colour differences across the visual EM spectrum and said that the DeltaE L*a*b* (1976) formulae were suited to compute it. I am not sure I did the right thing in the picture above (it’s still a bit complicated and obscure to me…) but this picture, as it would be printed by my Epson, should contain something close to the rendering of equally-colour-different EM bands. The picture contains 31 bands, like “keys” of a colour piano… The background is a 10% relative luminance neutral grey and each “key” has the same power.
Notice that the bands are very close in the yellow, and even closer in the blue-green areas: that’s where we are supposedly most sensitive to frequency-difference.
Notice that on the other hand the bands are far from each other in the red area.
Original spectral data: 31 gaussians with a variance of 1nm (click on the diagram to zoom)
Experimental studies with colour and light
As I see it, an experiment means precise physical actions set in accordance with a theory that describe their interaction. These actions refer to a question or to a hypothetic result, embedded inside the setup. An experiment requires a theory, a modus operandi, a setup, and a hypothesis.
My “cup of tea” is to make visual experiments with a scientific method. By studying the physics of coloured materials and lights, I invent ways to materialize abstract objects – or mathematical “concepts” of visual objects – without knowing in advance how the outcome will look.
As a way of working that generates otherwise impossible results, can inventing a process of “making” be, but a technical issue, an artistic research per se? Could my personal interest in physics, computer programming, digital printing, and painting become instruments for making visual experiences in a way that hasn’t been tried yet?
Traditional painting – as well as print-making – often ignore the light parameter: of course, a material picture is always the result of the illumination of coloured materials, but this very aspect is not much taken into account, and not studied for itself. The physical measurement of lights and coloured materials allow me to predict their interaction and thus, allow me to work on colour-perception with an original approach: I investigate how to “paint with lights plus paints.”
So far, I focused on creating a methodology, and the tools for an original visual language where the interaction between colours and light is key. In this context, I realized several series of studies and installation prototypes where I accumulated sets of experiments:
– Colorimetric pictures series, 2014 – the latest works, printed
– D65 series, 2011-2014 – hand-made paintings on paper
– Light Transformer prototypes, 2010-2014 – installations
The common specificity of each series is that they were attempts to formulate visual objects in a modern scientific language of colour theory. These attempts have been my first step toward an artistic medium that blends light and coloured materials in a single form.
Adrien Lucca, Oct. 16, 2014
“maquette” is a large-scale printed piece that will be installed in the Vrijthof Theater in Maastricht at the end of the week:
Adrien Lucca (Paris, 1983) lives and works in Brussels and was a researcher at the Jan van Eyck Academy in Maastricht. The work he is presenting is called Maquette. A grey “magma” of pixels, graded by lightness from black to white, wherein colorful and transparent visual objects emerge like waves on the surface of water. They are expressions of mathematical transformations of unequal size and visual magnitude, happening at random locations. The work covers a wall in Theater aan het Vrijthof. You are invited to come in, to come close and see its details. “Maquette” is a game of chance, a prototype for a multi-scale game of chance expressed in terms of spectral color variations.
This is the first Piece of a new Series of Unique Prints & Limited Editions – and a tribute to IVAN KLIUN (1873–1943)
The complete title: Tache de lumière – soustraction des fréquences du centre vers la périphérie (vers le rouge), 2500K
Meaning “Light Spot, Subtraction of [light] Frequencies from the Centre to the Periphery (to Red), 2500K [Kelvin Temperature Scale, or so-called “Colour Temperature”]
(click on pics to zoom)