Cultural Heritage Imaging

Canon Vs Nikon
June 1, 2012, 8:37 pm
Filed under: Commentary, Equipment | Tags: , , , , , ,

I was recently asked, ‘What DSLR camera is better for RTI data capture? ‘Canon or Nikon?’ The answer is like Godzilla Vs King Kong. Its gonna be a good fight.

The Short Answer is that either camera will work.

In the hands of a professional photographer, they are both very similar. The difference is the workflow – what you’re familiar with, what high quality lenses you own, and what equipment you’ve already got in your gear bag and studio ——— and what “Capture/acquisition Software” you decide to start a relationship with. (think Mind/Body – these two need to be pulling on the same oar)

Capture Software

Before you purchase a camera, you need to examine *how you’re going to interface with your DSLR when you’re shooting in *tethered* mode. Here’s the scenario, your stage is setup, your object is in place, you’re tethered to the camera via USB cable, and you launch your ‘capture software’ App. You need complete command of the basics : Composition, Exposure and Focus.

DSLR Remote Pro for Macs (Canon -> Mac)  |

The most stable Capture Software that we have used (bare in mind that we use Macs and Canons), is coded by a third party guy, Chris Breeze. He has taken the (Canon and Nikon) SDK and developed for a “combo” of Canon, Nikon – Mac, PC configurations. I’m not going to deep dive into the setups, but what I am going to state is that (at this moment in time), the Breeze software is stable, solid, is easy to use, and hardly *ever crashes. The user interface is Ok, a bit bare bones, but this tool gets the job done, and thats what we all want. Again, bare in mind that we use Macs and Canons (we have only used the Canon—Mac version). This software is installed on all our computers is our goto tool for image acquisition procedures.

The main user interface is a bit bare bones, but DSLR Remote Pro is solid and can handle minute focus adjustments needed for RTI production environments.

The last version of the Nikon Control Pro 2 software that I experienced worked really well, *except for the fact that it was difficult to check focus and scroll around bc that particular window has/had a restricted pixel size. It wasn’t as small as a thumbnail, but lets say that it did not take advantage of your screen size. All of the other functions were well behaved. Check it here:

The Canon Capture Utility (free with the purchase of a new camera) has a great interface, looks clean, works well, but it could be better, much better — it could be more stable. Sometimes it just flakes out and crashes. We used it for years with lots of happy moments, but towards the end we had a bitter break up. As RTI grew and we pushed the technology, we began to experience flaws. Specifically, with the ‘Live View Focus Controller functions’ (and its algorithms). Numerous frustrating crashes occurred when we asked it perform fine focusing adjustments in the ‘magnified mode’. This is pretty important considering that RTI *requires the subject to be in focus. Software crashes were even more problematic when we used a modified IR / UV camera — for some reason(s) that we can not explain, the software just didn’t adjust well to the different wavelengths of light under those conditions.

 A few more comments:

If you use ‘good Glass’ (think prime lenses+superior optics) both the Canon and Nikon are going to get you professional results. We know many many Canon RTI shooters as well as a few Nikon shooters (and hasselblad-er(s). I think that the majority of users tend to be Canon. When we are asked to purchase equipment for client(s) we always steer them towards the Canon family.

With that said, I have seen professionals purchase a suite of Nikon gear and then *re-convert all the new gear and go to Canon. (and from ongoing conversations, they didn’t go back to nikon).

At CHI we’re Canon all the way.

Thanks for reading, Happy F-stop.


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An Evaluation of Decorative Techniques on a Red-Figure Attic Vase from the Worcester Art Museum
September 6, 2011, 9:04 pm
Filed under: Guest Blogger, On Location, Training

In July we were back at the Worcester Art Museum Conservation lab to give a training in our IMLS sponsored 21st Century Museum Professionals program.  The Worcester conservation team was the first conservation lab to see the potential for Reflectance Transformation Imaging for art conservation back in 2006.  We built a lighting array for them, and delivered it and a training in May of 2008.

It was great to be back with that team and to see a bit of what they have been up to.  We were really impressed with their RTI work on Greek Vases.  They gave us permission to post a paper about this work so others in the RTI community can see it.

See below for more information on the publication:

An Evaluation of Decorative Techniques on a Red-Figure Attic Vase from the Worcester Art Museum using Reflectance Transformation Imaging (RTI) and Confocal Microscopy with a Special Focus on the “Relief Line”

Authors: Paula Artal-Isbrand(1), Philip Klausmeyer(2), Winifred Murray(3); 1,2,3 Worcester Art Museum, 55 Salisbury Street, Worcester, MA 01609, U.S.A.


Decorative features on a Greek red-figure stamnos in the collection of the Worcester Art Museum were examined using Reflectance Transformation Imaging (RTI) and scanning laser confocal microscopy. These two surface examination tools helped to answer questions relating to the decorative process, particularly the tools and techniques that Attic painters used to create the so-called glossy black “relief lines” and “relief dots.” This research also incorporated fabricated mock-ups to help understand the ancient technology. It was determined that the relief line was not produced by an extruded method, but with a brush made of one or very few hairs, an idea first proposed by Gérard Seiterle in 1976 and termed Linierhaar. It was observed that not one but two distinct types of relief lines exist: the “laid” line (proposed by Seiterle) characterized by a ridge running through the middle of the line and the “pulled” line (proposed in this paper) which has a furrowed profile. Both line types were reproduced with a Linierhaar. Additionally, relief dots were replicated using a conventional brush. Surface examinations of other red-figure vessels using RTI and the confocal microscope suggest these conclusions apply to vessels of this genre as a whole.

Download the Publication: An Evaluation of Decorative Techniques on a Red-Figure Attic Vase from the Worcester Art Museum using Reflectance Transformation Imaging (RTI) and Confocal Microscopy with a Special Focus on the “Relief Line”

Thanks again to the team at Worcester for their wonderful hospitality and collaborative spirit!  Keep up the great work.

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RTI Photography of the Red-Figure Pelike
June 10, 2011, 10:43 pm
Filed under: Commentary
RTI Photography of the Red-Figure Pelike

RTI Photography of the Red-Figure Pelike

As the RTI user community grows and becomes more viral, more discoveries are made. Once in a while, a blog comes across my desk that is worth sharing. This is one of them. Click on the jump to get there.

Thank you to Sue Grinols at FAMSF.

PS- nice blend map by the way (pretty good coverage for being set back on a table top!)

June 9, 2011, 10:14 pm
Filed under: Conferences, Training

June 8, 2011

Buzzed at AIC

At the recent annual meeting of the American Institute for Conservation (AIC) in Philadelphia, I was happy to see both past and future participants in the IMLS-sponsored CHI RTI training session program. I had to break the news to some interested parties that the sessions at the Worcester Art Museum and at the San Francisco Museum of Modern Art are already filled (with waiting lists) – but a few openings remain (apply here) in the sessions scheduled for the Smithsonian’s Museum Conservation Institute and the Indianapolis Museum of Art. Since AIC, several spots have already been taken.

Of course, conservators always want more visual information, and have been quick to understand the benefits of RTI for their work. Once conservators attend a CHI training session, RTI adoption spreads throughout the conservation community. At AIC, I heard several tales of conservators reaching out to their curatorial colleagues, presenting the extremely detailed technical art historical information to be gained from RTI. Curators were impressed! The ability to acquire this kind of detail is one of the hallmarks of RTI – in fact, in CHI’s Kress video Debbie Evans (paper conservator, Fine Arts Museums of San Francisco) mentions that RTI can allow the conservator to provide this important, detailed information to the curator. We look forward to more wonderful conservator/curator interactions!

By Elizabeth Peña

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Documenting a Reverse Glass Painting using Reflectance Transformation Imaging
April 1, 2011, 9:21 pm
Filed under: Commentary, Guest Blogger

By Guest Bloggers:

Golya Mirderikvand (Art Conservation, Queen’s University) and George Bevan (Classics, Queen’s University)

In the fall of 2010 a Master of Art Conservation Student, Paintings Stream, at Queen’s University, Golya Mirderikvand was confronted with a unique challenge: how to document a reverse glass painting before beginning treatment. From the recto the painting is convex with the paint being applied on the concave verso. Because the flaking and delamination of the paint was on the concave side, it was difficult to produce raking-light shots that would fully reveal the variation in texture without creating internal shadows that obscured the surface. Reflectance Transformation Imaging (RTI), which had already been extensively used by George Bevan in Classics, was then employed as the ideal way to document such a work.

Figure 1: House next to Stream, Recto

First some background on the type of work in question. Reverse glass paintings, or more commonly known by their German name Hinterglasmalerei, refer to the decoration of glass by painting or engraving metallic foil on the back of a glass panel.  Reverse glass paintings have a rich history with distinct variations in styles and techniques apparent from different periods.  Although their exact origins in Europe are uncertain, it is generally agreed upon that they were popularized in the 14th century, with the oldest surviving reverse glass paintings dating from the second half of the 13th century.

Figure 2: House next to Stream, Verso. Imaged under normal illumination

Paintings executed on glass panels are inherently fragile and susceptible to deterioration since they are not fired to allow the paint to become fused with the glass.  The primary mechanism of deterioration of reverse glass paintings is the detachment of paint films to the non-porous glass substrate. It has been speculated that a lack of proper preparation of the glass support in order to provide a better tooth, or a lack of application of a priming layer, or a combination of both, can lead to the delamination of the paint layers.  Other possible reasons of detachment could be as a result of condensation of moisture on the surface of glass, causing the paint films to release.  Internal and external factors contributing to the creation of interlayer shear forces can also lead to paint delamination.  This can commonly occur as a result of any backings or adhesives in direct contact with the paint layer from the back, or changes in relative humidity causing contraction and expansion within the paint layers.

Figure 3: House next to Stream, Verso. Imaged using RTI.

Figure 4: House next to Stream, Verso. Detail of upper left area, with normal illumination. Delamination and Blind Cleavages are identified within red ellipses.

Figure 5: House next to Stream, Verso. Detail of upper left area with RTI. Delamination and Blind Cleavages are identified within red ellipses

IMLS Sponsored 4-Day RTI Training at NYU
March 24, 2011, 11:18 pm
Filed under: On Location, Training | Tags: ,

Well, I love NY too.

In late March 2011, Mark Mudge, Carla Schroer, and Marlin Lum traveled to take a bite of the Big Apple and at its core was a 4-day RTI Training Session at the NYU Institute of Fine Arts Conservation Center. There, brilliant students and museum professionals participated in a 4-day hands-on RTI training. Each student learned how to capture, process, and view a Reflectance Transformation Image.

If you don’t know what a “RTI” is, read this, and you’ll have a better idea why it’s important:

“Reflectance Transformation Imaging (RTI) is a technology that has the potential to revolutionize documentation, treatment, and research of museum collections, while also promoting the integration of interactive images into the visitor experience. RTI enables museum professionals to examine an object’s very fine surface details using basic digital camera equipment and a few small additional tools.”

yup, we're capturing UV/IR RTis!

This training at NYU was partially sponsored by the Institute of Museum and Library Services. With the assistance of their funding, we are delivering 21st-century computational imaging tools into the hands of professionals who can make a substantial difference.


Brilliant Students(.)

As human beings on this earth for such a short time, we are striving to actually ‘make difference’ in people’s lives and in their careers. We want to make their work more meaningful and concrete. The final product is not just an interactive lighting map, but much more: knowledge, insight, value, and scholarly information, revealed by the artwork itself.

While on location at NYU, one of our students made an important comment. He pointed to the corner of the photo studio and said, “… that space there, that’s where, just last year, the photo enlargers were — we recently had them permanently removed.” (insert … silence, then echo laughter in a marble hallway)

RTI setup

NYU students during an RTI capture

That said, we’re moving right along into 21st-century computational imaging tools … we can now know more about our artwork than ever before.

A special thank you to NYU and *Hannelore Roemich.

Thanks for reading.

Marlin Lum
Imaging Director
Cultural Heritage Imaging.


PS: If you want to learn how to capture, process, and view RTI lighting maps, apply to the free IMLS-sponsored training sessions. Click here to get the details.


Discoveries made at every viewing!

Free IMLS Sponsored 4-Day RTI Training Sessions
March 23, 2011, 10:11 pm
Filed under: Training, Uncategorized, Workshops

“21st-Century Museum Professionals Grant Program”

Institute of Museum and Library Services
National Leadership Grant Project

Thanks to a generous grant from the Institute of Museum and Library Services 21st Century Museum Professionals program, CHI is pleased to present a series of FREE training sessions in Reflectance Transformation Imaging (RTI), graciously hosted by the following institutions:

Worcester Art Museum: July 11-14, 2011

San Francisco Museum of Art: Aug 15-18, 2011
Smithsonian Museum Conservation Institute: Mar 5-8, 2012
Indianapolis Museum of Art: Sept 10-13, 2012

Learn More. Space is Limited. Apply NOW.