Back to

Seeing into the Infra Red: On Cameras, Connections and Conservation Documentation Part II

The following post was written by Charles Falco (pictured below), Professor of Optical Sciences; Physics and UA Chair of Condensed Matter Physics.

Charles Falco

Professor Charles Falco

OK, yesterday Richard gave you his version of events.  Today, it’s my turn.

Part I: Making the Connections

My Background

The year: 1960
The place: Ft. Dodge, Iowa
Richard started his story ten years ago in Madrid.  I’ll start mine fifty years ago in Ft. Dodge.

I’ve been keenly interested in images since early childhood, starting with an old Kodak box camera, and advancing to my first “serious” camera when I was twelve. This involvement with creating and manipulating images using various processes — photography, cyanotypes, silk screening, etc. — steadily expanded as I got older, to the point that by age 30 I owned at least 20 lenses ranging up to a 800 mm super-telephoto, as well as had designed and fabricated various pieces of specialized photographic equipment for my imaging experiments.

The infrared camera described in this blog is the most recent piece of fabricated/altered imaging equipment dating back to an enlarger I made in high school by modifying an old bellows camera.Although I got my Ph.D. in physics, and have worked in experimental physics my entire career (first at Argonne National Laboratory, and since 1982 as a professor of optical sciences and of physics at the University of Arizona), I also have had an interest in art that dates back to childhood.  By age 30 I had visited over 25 art museums in eight countries, always using any free time during travels to physics conferences to visit art museums.  And motorcycle museums.

Like my interest in photography, I have been a participant in art as well as an observer.  In the May 14, 2007 issue of The New Yorker Magazine, Peter Schjelhahl wrote “An efficient test on where you stand on contemporary art is whether you are persuaded, or persuadable, that Chris Burden is a good artist. I think he’s pretty great.”  Burden is perhaps best known for his November 1971 conceptual art piece ‘Shoot’, in which he had himself shot in the arm.  A month earlier, for his piece ‘220’, he and three others spent the night on wooden ladders in a gallery filled with 12″ of water into which he had dropped a 220-Volt electrical line.  I was one of those three participants.

Jumping ahead a few decades, in 1997 I was asked to co-curate the Solomon R. Guggenheim’s The Art of the Motorcycle exhibition that opened in 1998, and which set an all-time attendance record for that museum.  I shared an award for this work from the U.S. Chapter of the Association Internationale des Critiques d’Art with the architect Frank Gehry, the then-director of the museum Thomas Krens, and my co-curator Ultan Guilfoyle.

Making a long story short, thanks to Ultan Guilfoyle, in 2000 I was introduced to David Hockney by Lawrence Weschler, who had written a story about him in the January 30 issue of The New Yorker Magazine.  This resulted in the most intense period of collaboration of my entire scientific career.  One consequence of our collaboration was that I was invited to the National Science Foundation in 2006 to give the Distinguished Lecture in the Mathematical and Physical Sciences.  Zina Deretsky attended that talk, resulting in her arranging for me to speak at the annual meeting of the Association of Medical Illustrators, resulting in me meeting Richard McCoy, resulting in this blog.

Artwork in the Infrared

In the spring of 2008 I realized that since modern digital cameras use silicon CMOS or CCD sensors, and since silicon is sensitive reasonably far into the infrared (to ~1100 nm, whereas the visible ends at ~750 nm), a suitably-modified camera might allow the capture of high resolution infrared photographs — “IR reflectograms” — of works of art.  The reason IR reflectograms are of interest for art is that many pigments are semi-transparent to infrared light, allowing such light to penetrate through these pigments to reveal features that are not apparent in the visible.  Such features can include defects in the canvas or board (Figure 1),


Figure 1

areas that have been repaired by overpainting (Figure 2),


Figure 2

or underdrawings made on the white gesso (Figure 3).


Figure 3

In addition to paintings, the camera provides useful information on 3-dimensional objects (Figure 4).


Figure 4

However, the IR sensitivity of the silicon sensor is only one factor in the operation of an imaging device, so the only way to know if such camera would actually provide useful information for works of art would be to modify one and characterize all of its relevant features.

I rationalized spending the money for this by telling myself that, even if it proved useless for extracting useful information from art, I still could use it for general infrared photography.  However, my understanding of the technologies involved gave me a great deal of confidence my money would be well spent. As a result, a technical description of this high resolution infrared imaging instrument just appeared as an invited paper in the July 2009 issue of the ‘Review of Scientific Instruments’.  You can download a copy of it from the link at the bottom of my art-optics web page.

Figure 5

Figure 5

I conducted the first tests of this modified camera in my own university’s art museum, and immediately discovered interesting new information in some of the IR reflectograms.  As an example, the lines in the underdrawing in Figure 5 that are revealed in the IR converge to a well-defined vanishing point, showing that this particular artist understood the laws of geometrical perspective that had only recently been articulated.  This is information that no one ever could have known before.

The Infrared of Indiana

Having determined that the modified camera was indeed capable of extracting useful new information from paintings, I took it with me to Indianapolis where I was to speak at the Association of Medical Illustrators.  Basically, the reason I brought it was to gain experience with it when “on the road,” vs. in the relatively controlled environment of a museum located only a few hundred yards from my office.  However, I didn’t know I would have the opportunity to test it at the Indianapolis Museum of Art against paintings recently studied with a special-purpose IR camera, so the introduction to Richard McCoy and David Miller made by Zina Deretsky was pure serendipity.

The results initially were disappointing to all of us when looking at the freshly-captured images on the camera’s LCD screen, but we were very pleasantly surprised when we pulled them into Photoshop(R) on one of the museum’s computers.  The reason for the difference in appearance is that the resolution of the LCD screen is ~10x lower than the resolution of the actual images.  As a result, even features that are quite apparent in the images captured by the camera usually are barely, if at all, visible on the LCD screen.

Since that first “in situ” test in Indianapolis in July 2008, I have captured IR reflectograms with this camera in eleven art museums on three continents so far.  One of my favorite incidents involving it was an evening talk I gave at the Minneapolis Institute of Arts, in which I discussed some of features revealed in one of their paintings (a Pissarro) by an IR reflectogram.  I captured that image at 11:31 a.m. and talked about it at 7:20 p.m., which must be some new record for the fastest time between extracting new scientific data from an artwork and “publishing” the results.  You can see this talk on Youtube, and my 2 minute discussion of the IR starts at 50′ 40″ into the video.

I should note that nothing revealed by that IR reflectogram was particularly spectacular.  But, I already had data on another Pissarro painting in my talk, so this was a great opportunity to work in something previously unknown about a painting in that museum’s own collection.  I also gave the audience the homework assignment of remembering what I had just showed them, and after my talk going back to the actual painting to look for the features themselves.  So, in addition to extracting useful new data from paintings, this camera also can be used to engage an audience in art history in new ways.

Filed under: Art, Conservation

One Response to “Seeing into the Infra Red: On Cameras, Connections and Conservation Documentation Part II”

  • avatar
    Edwin Herdman Says:

    Modifying digital single-reflex cameras for fine art photography has been a hot topic for amateurs attempting to follow in the footsteps of Dr. Robert Wood for years now. Since roughly 2002 I have had access to the Sony F707, a cult IR crowd favorite which flips a low-pass filter out of the way for shooting infrared pictures in dim to nighttime scenes. Its proponents may well ask: What about saving even more money and using a compact camera? Unfortunately, my experience with the system seems to demonstrate that non-DSLR camera systems are not appropriate for anything far beyond casual IR photography, let alone critical or scientific work.

    That even assuming that modern cameras allow an easy IR mode, which they don’t seem to do since the early 2000s. I suspect this helps assist makers in clamping down on IR polluting visible spectrum photos, color balance, and changing focus points; improves reliability (no moving “hot mirror” low-pass filter for blocking infrared), and also to avoid press issues such as Sony reportedly faced after a rash of “Sony cameras see under clothes” sensationalism is said to have tarnished the feature.

    The answer to the question is apparent from the paper’s discussion of the appropriate wavelengths to allow through the filter for this purpose, but although that has been solved by enthusiasts using filters outside the camera body (actually not a huge problem with the F707), other problems tend to abound when using a compact camera with non-removable lenses that happens to have the IR sensitive properties of CCDs exploited for easy night shooting capability.

    The F707 did enjoy a cult following for years due to its IR photography capability, but it also needs a bit of extra investment to take IR-only photos (such as a ND filter to overcome an arbitrary 1/60 second maximum shutter speed in this mode (meant to prevent daytime use), or an ultraviolet filter which leaks some IR to act as both an ND filter and high-pass filter, such as a Schott UG1 suggested by Bob Fosbury on his webpage discussing shooting with the F707).

    Even then it is limited to being used only in an automatic mode with a shutter speed of 1/60 or slower, and there are other problems as well (a zoom lens with a narrow aperture, small sensor, high gain applied for IR capture, and other problems such as TIFF or JPEG only instead of RAW and other functionality or usability issues). An actual DSLR will provide the photographer with a wider choice of lenses, and art studies seem ideally suited for a fast prime such as my Canon 50mm f/1.4, not a compact camera’s softer zoom. Fundamentally, the F707’s IR modes were a quirky extra bullet point that is not calibrated for scientific use, and seems to have been a fairly short-lived trend; from what I can tell the Nikon Coolpix series around the 950 and 4500 model marks had some IR capability as well, but newer compact cameras with up-to-date sensors seem to have done away with the feature and any inherent complexity or reliability challenges.

    It’s great to use something as flexible and affordable as a DSLR for this serious work. When it’s newly obsolete, I might inqure about having my Canon T1i converted to infrared – being able to do studies like this in addition to tilt-shift infrared landscapes all in one camera body is serious value for the photographer. (Incidentally, the T1i has proved sufficient for my needs thus far, and it has already dropped in price over $200, I’d guess due to Canon concerns about the market segment it covers; it seems fairly equal for regular photography to the 50D which has held its price better).

    Thanks to Mr. McCoy and Mr. Falco for this engaging series, and especially for Mr. Falco’s paper on infrared photography. There are many reputable providers of infrared conversion services, but with this paper the scientific and practical details are no longer a matter of guesswork but of actual figures.

  • Trackbacks