Tag Archives: UV Radiation

Fun with PhotoDoc: Multispectral Imaging with MISHA (Edition 13)

As mentioned in a previous blog post, Andrew and Naomi from Case Western Reserve came to the lab in late February to demo the MISHA portable multispectral imaging system, made possible by a National Endowment for the Humanities (NEH) Research Grant awarded to the Rochester Institute of Technology. In total, Naomi and Andrew imaged five objects from the Public Library, UC Libraries, and one of our third-party institutional clients. Imaged books included, one Otto Ege item, two Book of Hours, one undated Latin music manuscript, and a Pentateuch volume from Hebrew Union College. In all, thirteen separate capture sessions were carried out for the five objects. Afterwards, the raw data from the capture sessions was shared with the Lab via OSF (Open Science Framework) so that I could process the data in the NEH grant supported open access RCHIVE (Rochester Cultural Heritage Image processing and Visualization Environment) software.

The image gallery above shows the recto of leaf 32 from the Public Library’s copy of Fifty Original Leaves from Medieval Manuscripts, Western Europe, XII-XVI century, by Otto Ege.

While each of the capture sessions took only two minutes to complete, I found that processing the raw data took me a bit longer to figure out. Processing the data felt very similar to using CHI’s RTI Builder and Viewer software. However, in this situation I did not have a week-long training opportunity to learn the ins and outs of the software and its functions. For the Spectral Analysis App, I had only a couple of brief documents to refer to, so the learning curve was a little steeper. I also experienced some issues with the software while processing the data with the flatfield files provided from the capture session. But in the end, the processed files seemed fine without the flatfield data, so it all worked out.

RGB image of a parchment page from a Pentateuch volume belonging to Hebrew Union College — RGB representation

Multispectral image of a parchment page from a Pentateuch volume belonging to Hebrew Union College — RGB representation

The above image gallery depicts a leaf from Hebrew Union College’s Pentateuch Ms. 1 with adhesive staining, tape, and prior repairs.

What I discovered through processing all the MISHA data and then comparing it to the existing specialized imaging done in the Lab was that the suite of imaging we do in the Lab is very well rounded and, in general, suits our needs and our clientele quite well. In many cases, our results were at least comparable, if not better (specifically within the UV wavelengths) than the results accomplished using the MISHA. And, especially with our UV workflow, though our current capture time might be slightly longer than that of MISHA, the data processing time is significantly shorter and, in the case of UV especially, the side-by-side results of the accurate normal illumination next to the full color UV image(s) is ideal for our purposes.

RGB image of an opening of a Book of Hours with scraped parchment and illegible text — RGB representation

Multispectral image of an opening of a Book of Hours with scraped parchment and illegible text — RGB representation

The images above show an example of scraped text on parchment from UC Libraries Hours of the Virgin from 1475, currently in the Lab for treatment. Compare these MISHA generated images to the documentation performed by Catarina Figueirinhas and myself using the Lab’s equipment and processes below.

Normal illumination image of the same illegible text — Normal illumination

UV image of the same illegible text — Normal illumination

That said, I am fully aware that not everyone has access to the equipment/training that I have been fortunate to curate/experience over the last five plus years. Also, not everyone uses their finished data exactly how we do. For instance, the needs and expectations of a conservation lab and cultural heritage institutions can be very different. Even within the conservation field, how we use the data provided by specialized imaging in our hybrid book and paper lab is quite different from the kind of data needed by a fine arts conservation lab. Ultimately, I think the core audience for a system like the MISHA system is an organization looking to expand their suite of imaging services, or an institution with no multispectral imaging infrastructure interested in imaging collections in a quick and easy manner. Though for the latter, I would say that there is a big learning curve in manipulating and processing the data, but if greater focus is put into making the software and processing steps user-friendly, especially to novice users, it is completely manageable. And if this step is taken, I think the system could help a lot of institutions dive deeper into the materiality and history of their collections.

The images above depict another example of faded, scraped text. This flyleaf is from an undated Latin music manuscript that is part of the Public Library’s collection. The images below represent imaging done by the Lab, both normal illumination and UV radiation, with the goal to increase the legibility of the inscription.

Normal illumination image of faded text from a parchment manuscript — Normal illumination

UV image of faded text from a parchment manuscript — Normal illumination

In the end, multispectral imaging is just plain FUN! So, the idea of making it more accessible to a wider audience is extremely exciting and I think the work that NEH, RIT, and colleagues like Andrew and Naomi are doing to share the power and wonder of multispectral imaging is amazing. The idea of a portable multispectral imaging system with free processing software that does not take a PhD to use is boundary-breaking, and it gives us a glimpse into a future of accessible and exciting imaging, which thus allows us to see and understand more of the past. I will always be an advocate for that kind of imaging!

Jessica Ebert [UCL] – Sr. Conservation & Photographic Documentation Specialist

Fun with PhotoDoc: New and Improved UV Setup

You may recall back in September of 2018 when we shared an article I had written in our UC Libraries’ newsletter about photographic documentation in the Lab and a recent workshop I had attended through FAIC: http://libapps.libraries.uc.edu/source/photo-documentation-in-the-preservation-lab/ If you missed it, basically the workshop focused on a standardized and replicable UV/visible fluorescence documentation workflow, and was taught by Conservator Jennifer McGlinchey Sexton at Duke University. It was a fantastic workshop and I came back from it with a plan for a new UV workflow and a list of equipment for an improved UV setup. However, conservation photography equipment can be pricey, especially when you are embarking on improving a very specialized setup, like UV. On top of that we had just included a Near Infrared workflow into our photography repertoire and our budget was feeling the strain. So we took the smart approach and slowly bought equipment, here and there, when the budget allowed. Finally, we now have all the equipment we need for the new setup. Check out the results from today’s session:

Left: normal illumination, Right: UV radiation

Lucky for me, when it came to refreshing myself on the actual workflow I had learned at Duke the binder that Jennifer had put together for each workshop participant was incredibly thorough and all I needed to replicate the workflow in the Lab. Before we dive into the aspects of the new workflow and why it is “improved”, let’s discuss our previous workflow for a second. Like most conservation labs, we refer to The AIC Guide to Digital Photography and Conservation Documentation (currently on sale for $20!) for almost anything PhotoDoc-related. For UV, the book details the different types of ultraviolet radiation, various types of UV lamps, safety (both for the object and yourself), setup, filters, and workflow. In this volume the basic workflow describes using the camera’s “shade” white balance setting and then adjusting the temperature to 10000K and the tint to +35 in CameraRaw. Exposure is determined by the photographer using visual cues alone, as there is no way to white balance using a standard color checker; the Neutral 8 (N8) patch will no longer be neutral grey under UV fluorescence.

While this workflow produces very usable images that illustrate the fluorescence of materials, inks, pigments, adhesive and staining, it is subjective and makes replication of results more difficult. While our prior workflow for UV photography could use improvement, the workflow itself was not the main issue, in fact, this is the workflow used in many other labs. The problem child of our setup was the equipment, and I’m sure any lab trying to piece together a completely brand new PhotoDoc studio (which happened six years ago for us) on a budget can relate. Behold our previous “UV” lamps, which I affectionately referred to as the “Home Depot setup”:

Good ole black lights! Though, unfortunately, we did not have a velvet Elvis black light poster hanging in the studio to really take full advantage of these babies.

If we’re being honest, these low-pressure fluorescent lamps were super cheap and served their purpose for 6 years. Shooting with them was a bear; since the intensity was very weak, I would have to shoot with both lamps and we did not have any clamps to hold them in place. I had to either get someone to assist me or, once I got a wireless mouse, I got even more creative (ask me about it sometime – it’s pretty funny). The downside of these inexpensive lamps is the significant and noticeable visible light leakage. Since the fluorescent tubes are not properly filtered, the image you are left with has a blueish-purple cast to it:

Notice the blue cast to the background in this image.

Now onto the new setup! The main components include:

1 – REL C4 Magnum-GO lamp* – this is an LED lamp with a peak output of 368nm. It comes with a filter over the radiation source, therefore eliminating visible light leakage from the lamp.
Taget UV and UV Gray Card – this color checker and gray card are specially designed for UVA fluorescence photography and allow you to white balance prior to imaging (gray card) and identify the RGB values (target).
Impact Super Clamp – to hold lamp for hands-free tethered imaging
Filters (which you should have regardless of your setup, but we did not have them previously) –
- 2E – cuts UV and blue
- PECA 918 (or equivalent, we have a Hoya IR Cut filter) – cuts IR even more
- We also purchased an adapter in order to fit both filters on our smaller 50mm lens
UV Glasses (always part of our setup but worth mentioning) – safety is very important and we purchased these goggles because they easily fit over eyeglasses.

Right to left, top to bottom: filters, SuperClamp, UV Glasses, Target UV, UV Gray Card, REL lamp

Fun facts about the REL lamp: The intensity of the lamp and the handle make it great for quick examination. It has a normal LED built in as well and you can have both functions on at the same time, making it easier to see if you’ve turned your studio lights off or if you want to do a quick comparison of normal illumination vs UV radiation. As with any UV radiation source you want to keep it away from your object until you are ready to image. When using a radiation source you also want to let the lamp warm up for at least one minute before imaging (away from the object or with the object covered). This is because when a lamp is initially turned on it can emit up to eight times more UV radiation, and allowing the lamp to warm up gives the output levels a chance to even out, making it much safer for the object.

Fun facts about the Target UV & UV Gray Card: I know the target and gray card are extremely expensive and not feasible for everyone, but there are definitely advantages to them if you have the budget to invest in the pair. Not only do the target and gray card allow for white balancing, thus giving you a more accurate color temperature and color representation, but the target is also double-sided and has 4 separate intensity levels: low, medium, high and ultra. This basically means that you can image a wider variety of fluorescence intensities without sacrificing exposure or color representation. For example, if you have an object with a layer of varnish on it that only mildly fluoresces, you would probably use the “low” intensity patch to white balance, whereas if you have an object with optical brighteners (extreme fluorescence), you would likely use the “ultra” intensity scale. This makes it very handy if you have one object that has multiple materials/inscriptions/staining that are fluorescing at very different intensities.

Overall, I am very happy with the new setup and workflow, and I am looking forward to using it more and more in the future.

*In the workshop we used by the REL C4 Magnum LED lamps and these UV Systems SuperBright 3 LW370 lamps. Both worked beautifully but it seemed as though two of the UV Systems lamps would be needed while I could get away with just purchasing one of the REL LED lamps. The UV Systems lamps would have also required a much more robust mounting system beyond the SuperClamp because of their weight and orientation.

Jessica Ebert [UCL] – Conservation Tech/Photographic Documentation Tech

Fun with PhotoDoc – In the News (Edition 9)

Check out this new article written by our lead photographic documentation technician, Jessica Ebert, on the exciting world of photographic documentation in the Preservation Lab: http://libapps.libraries.uc.edu/source/photo-documentation-in-the-preservation-lab/

This is an image of a painting of a young woman done in a variety of white pigments. The image depicts the painting under ultraviolet radiation. This particular painting was painted by the artist under UV radiation, so it is not until it exposed to UV radiation that the viewer is able to see the full extent of the detailed work.

This is an example of one of the pieces that was photographed under UV radiation in a recent workshop Jessica attended through AIC. In this workshop at Duke University, taught by conservator Jennifer McGlinchey Sexton, participants learned how to identify the best UV lamps for conservation documentation, how to test for visible light leakage, and how to standardize UV documentation workflow using the Target UV (to the right of the painting).

Fun with PhotoDoc – Edition 1

Since I am the conservation technician who carries out most of the photographic documentation in the lab I think that pretty much all PhotoDoc is fun. With all the different tools in the toolbox it really doesn’t get much better than when you get to bust out the ultraviolet radiation to reveal something that is otherwise not so obvious under normal illumination (like a stain, handwriting, etc.). And then when you can transform those normal and UV before photos into a gif…well, that just makes for a fun Friday, if you ask me!

This photograph is part of the Henry R. Winkler Center for the History of the Health Professions collection and arrived in the lab with the original glass broken and partially attached to the photo. It is obvious under normal illumination that the photograph endured some kind of spill or water damage, but under UV florescence you can better make out the path that the water or perhaps beverage created and even note splotches of possible mold damage (which flourese purple). Now that’s it’s photographed I’ll turn it over to Ashleigh, our conservator, to determine what’s happened to this poor thing and the best course of action when it comes to treatment and storage.

Jessica Ebert (UCL) – Conservation Technician