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Technical Photography

If you look up #mygirlwiththepearl on Instagram, you’ll see hundreds of creative photos inspired by the Girl with a Pearl Earring. In our files in the conservation studio at the Mauritshuis, we also have hundreds of photos of The Girl taken over the course of the last century. It’s important to document how a painting changes over the course of time: especially before, during and after a conservation treatment. As time passes, the materials in a painting can change, but camera equipment also improves. Nowadays, digital photography and computer-assisted analysis provides lots of possibilities for taking and using these photos.


Abbie and René use a Colour Checker to calibrate the digital camera before technical photography. Photo: Jaap Hoogerdijk.

Before the Girl with a Pearl Earring was brought down to the Golden Room for the technical examination, she spent a night in the conservation studio. There, she was unframed, measured, examined and photographed. René Gerritsen and Jaap Hoogerdijk took photos of her under different kinds of lighting conditions and radiation sources.


Electromagnetic spectrum

What do I mean by ‘radiation sources’? The electromagnetic spectrum describes the different lengths of energy waves (radiation) that travel from the sun to the Earth. Certain materials in the painting react to specific wavelengths, and can be detected using special cameras and filters that isolate specific parts of the spectrum. The range of wavelengths that are most useful to conservators are inside the red box: x-rays, ultraviolet (UV), visible light and infrared (IR).

X-ray

An x-ray of the Girl was made in four parts. A portable x-ray machine was aimed at the painting while The Girl lay carefully on the floor, with the x-ray film and a lead plate underneath. After developing the x-ray films, they were examined on a light box. The parts of the painting that absorb the x-rays – like the nails that hold the canvas around the edges, and the lead white in the paint – appear white. Tiny areas where the paint is damaged appear dark. In the coming days, I’ll tell you more about the x-ray as I describe Vermeer’s canvas, ground, and use of lead white. 
Click here to read more about how x-rays are used to examine paintings.


The Girl lies under the x-ray machine on a soft piece of foam. René places an x-ray film behind her. The x-rays go through some parts of the painting and are absorbed by a lead plate in the floor.


X-ray. Photo: René Gerritsen Art & Research Photography

Ultraviolet fluorescence (UV)

Ultraviolet light is similar to the ‘black lights’ you used to see in clubs, coffee shops and haunted houses. If you shine a UV lamp on the painting, some of the pigments and dyes that Vermeer used to make his colours are ‘excited’ by the UV rays. For example, her lips contain red lake, which has a pink fluorescence. UV also reveals the materials that were applied during later restorations. The layer of varnish on the surface fluoresces green, and retouchings appear darker than the original paint. The damage in her eye, which was retouched in 1994, appears black in the UV image. 
Read more about ultraviolet (UV).


UV photo. Photo: René Gerritsen Art & Research Photography 

Visible light

Daylight lamps were used to take a ‘visible light’ picture. We can zoom so far into the high-resolution photos that we can see that her eyelashes are made up of tiny black hatched lines.

For the ‘visible light’ photo, we position lamps on either side of The Girl to make sure she is lit evenly. If we shine one bright light from one side of the painting at a sharp angle, we can take a ‘raking light’ photo. This shows the 3-dimensional relief of the painting, including the differing heights within Vermeer’s brushstrokes, and the cracks. In a couple of weeks, I’ll devote a blog post to the topography of the painting and the cracks.


Polarised light was used to minimize reflection. Photo: René Gerritsen Art & Research Photography


Raking light. Photo: René Gerritsen Art & Research Photography

Infrared (IR)

Infrared reflectography can be useful for revealing materials containing carbon black that sit at or beneath the surface of the painting. Some layers beneath The Girl’s clothing contain black pigments (which I’ll describe in a later blog entry). The black pupil of her eye appears dark in the infrared image.
Other infrared techniques will be used as part of the near-infrared imaging later this week.


Infrared image. Photo: René Gerritsen Art & Research Photography

Behind the curtain

Each of the pictures above is made up of many high-resolution digital photos. Afterwards they were stitched together on a computer to make a digital image that is many gigapixels in size, but can be viewed and loaded quickly in your browser. 
Rob Erdmann, Senior Scientist at the Rijksmuseum, developed a ‘curtain viewer’: a visualisation tool that lets us organise, overlay and compare these digital images. As our examination of the Girl with a Pearl Earring progresses, we will add new data to the curtain viewer, and compare them like they’ve never been compared before. 

References

  • The Mauritshuis: Second Canvas app for your phone or tablet lets you switch between a visible light and infrared image, and zoom in.

Acknowledgements

  • René Gerritsen Art & Research Photography: René Gerritsen and Jaap Hoogerdijk
 

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