Thursday, 31 May 2012

Choosing a Camera for Highlight RTI

I am in the process of ordering Highlight RTI (H-RTI) equipment, mainly for use in museum contexts on portable and fixed artefacts/material surfaces. Happily, I have the funding to assemble quite high quality kit -- which is simply brilliant, thanks to the Marie Curie Actions COFUND program and the Dahlem Research School here at Freie Universität.  

Nikon D3X, 24.5-megapixel FX-format D-SLR
In researching the best camera for the job I am leaning towards Nikon D-SLRs instead of Canon (though Canon is perfectly fine for RTI, the camera choice of  RTI experts Cultural Heritage Imaging). I was previously using the Nikon D3X for dome RTI as part of the University of Oxford's RTISAD project. The D3X (right) is the fabulous beast I also took to Qubbetel-Hawa*, Aswan for the SCA / University of Jaén project, as mentioned in a previous post.

The D3X is a real workhorse and certainly robust enough for the rigours of fieldwork in Egypt and it has provided superb results. But the model is now about 3 or 4 years old, puts quite a hole in the ol' wallet, and has more bells and whistles than I need for tripod-mounted shooting. The D3X is good for action shots, and sports photographers, etc. love its speed, but archaeological artefacts tend to hold quite still...mind you, if an artefact does start's probably time to drop the camera and run!!

Anyway, what is also persuading me to go for a Nikon is that they have just come out with a new model: the D800 (and the D800E). This is currently one of the best cameras in the world, offering a whopping 36.3 megapixels and major improvements on the ISO front, as this Nikon D800 ISO comparison demonstrates.
Feast your eyes!: Nikon D800 (800E), 36.3-megapixel FX-format D-SLR
For RTI, capturing surface detail as accurately as possible is the name of the game (recording empirical provenance is critical, too: see Digital Lab Notebook). Super high quality capture of material surfaces means avoiding cameras with an anti-aliasing or low-pass filter. This filter, as I understand it, is designed to blur the image slightly to avoid things like moiré**. This is described in an easily understandable way on this website. The upshot is that the D800 will blur the image slightly and the D800E will not. "The benefits of the D800E are also most noticeable when working with the RAW (NEF) file format" and this is the archival-quality-future-proofing-sustainable file type one should shoot in doing RTI to get crisp details of surface morphology. Thus, the D800E (3.219,00 €...a hefty price tag however you slice it) is a camera that is well suited for RTI, unless you can afford a big gun like the D3X (5.900,00) or the new D4 (5.929,00 €), or you prefer to go with Canon (CHI nod approvingly, I'm sure).

But -- and there's always a but -- the D800/D800E has only just come out, and with some delay. Deliveries to suppliers in the US and Europe are coming in drips and drabs (are Euro 2012 and London Olympics photographers hogging them all?). As I really really need to get on with my museum research visits -- the clock is ticking away with a vengeance -- I am starting to panic a bit. If a D800E doesn't become available very very soon indeed, I may have to shift gears and go with a Canon (mayhap a 22.3MP EOS 5D Mark III?) or rejig my budget big time for a Nikon D3X or D4. Guess I'll give Nikon another couple of weeks...

* Scroll down on diary entry for 23 FEB 2012.
** NOTE: I am NOT a professional photographer (yet) but Nikon staff, online forums and colleagues have been super helpful with advice. And you, dear reader, are always welcome to add constructive comments on, corrections to, and additional insight into the info presented here!

Wednesday, 4 April 2012

Visualising ancient Egyptian artefact surface transformations

These past several days have been largely occupied with preparing and delivering a conference paper at ‘The Computer Applications and Quantitative Methods in Archaeology’ (CAA) 2012 at the University of Southampton.

As mentioned in a previous post, I am researching early Egyptian (and Mesopotamian) image bearing artefact surfaces in order to understand how they were formed and transformed through scribal and artistic activities. Taking the example of elaborate carving on a Late Predynastic (c.3100BCE) Egyptian mudstone palette, namely the so-called Hunters Palette,
I am investigating evidence for its creation through close analysis of the carved surface using Reflectance Transformation Imaging (RTI) data*.
Hunter's Palette: relief carved mudstone, said to come from Tell el-Amarna.  Photograph © Trustees of the British Museum; drawing from Smith 1949; both from Davis 1992.
My aim is to answer questions such as: What tool and carving technique types can be discerned? What stages in surface preparation / carving can be identified? To what extent was the carving planned out prior to execution?

While beginning to unpick these issues -- studying my RTI data in RTIViewer and slowly moving the virtual light around -- I found intriguing new evidence erasure and recarving!**

This 'diffuse gain' RTI photographic output is a detail of the the lower right side of the upper right palette fragment (above). It shows the 'ghosts' of previous carving and what may be the original path of the rope (indicated by three parallel arrows), and the original position of the hunter's 'tail' (indicated by a horizontal arrow) which is attached to the back of his kilt and abuts the rope (Piquette and MacDonald Forthcoming).
In order to visualise the palette’s surface further and characterise these transformations more fully, I’ve teamed up with Lindsay MacDonald, a researcher in Geomatic Engineering at UCL. Using his mathematical and computing expertise (Lindsay specialises in colour imaging, vision science, digital photography and computer graphics) and my raw RTI data (i.e. the series of photographs I took at the BM in late 2010 using the RTISAD project's Oxford RTI lighting dome), Lindsay has been experimenting with new visualisations of the erased/recarved area using different kinds of algorithmic rending or AR (fear not - if mystified, click the link and become de-mystified via a neat and tidy description with examples courtesy of the good folks at Cultural Heritage Imaging!).

Depth map of Hunters Palette with section profiles (Piquette and MacDonald Forthcoming).
One result of Lindsay's algorithmic rending (AR) work was the depth map, presented above as a grey-scale image. The deepest areas are darkest and the highest are lightest. The red lines indicate the positions of a vertical and a horizontal cross-section. The graphs at the left and bottom show the corresponding elevation profiles (scale in mm). In the vertical section it can be seen that the height drops by about 10mm in the area below the hunter’s rib cage -- possible evidence for recarving that was not apparent from the amalgamated RTI image. In the horizontal section there can be seen a slight furrow of depth approximately 3mm in the background region above the 'original tail’, further supporting the observation that this area of the surface has been recarved.

These and additional results from our collaborative work on the Hunters Palette and its surface transformations formed the topic of our paper at CAA 2012 in Southampton (check out the abstract). We're now in the process of finalising this piece of research and writing it up for publication, but we have plans to undertake the further study of early Egyptian inscribed and decorated artefacts surfaces using both RTI and AR -- with many exciting results anticipated!

* Thanks are due to the British Museum and the Arts and Humanities Research Council’s Digital Equipment and Database Enhancement for Impact (DEDEFI) scheme.
** Not quite clear on what I am describing? You can have a go easily enough using RTIViewer on your PC or Mac. Download the Open Access ( = free) software and 'test drive' it on the papyrus or rock art examples provided. Try'll like it! :-) And then let me know what you think!

Tuesday, 13 March 2012

Reflectance Transformation Imaging (RTI): A taster

In my previous post I referred to the way in which the digital imaging technique Reflectance Transformation Imaging (RTI) can make visible surface marks which may not be apparent with the naked eye -- or at least enhance features that are difficult to see depending on lighting conditions and how you look at an object (more on seeing/looking in another post, but just to highlight here that this is not necessarily a neutral activity!).

I am exploring the possibilities of inserting an RTI viewer into this blog, or otherwise linking to one in order to show examples of my RTI results. In the meanwhile, if any reader comes across a solution -- please do let me know. For those unfamiliar with the kinds of results one can achieve with RTI, here is one of my favourite examples from the AHRC-funded University of Oxford and University of Southampton RTISAD project I worked on in 2010-2011 (for more information check out our interim report).

Here is a detail of a stunning portrait from the mummy of a Roman woman who lived around c.160-170AD. She may have been buried at El Rubaiyat in Egypt where the portrait is thought to have been found (and now housed in the British Museum). Her portrait is made with encaustic on limewood and added gilding. The top image is an RTI output with even 'default' lighting; the middle image shows the 'diffuse gain' rendering mode which enhances the perception of surface shape features for interpretive purposes; and the lower image exemplifies the 'specular enhancement' mode which renders the shape-based reflections to also enhances the perception of the surface shape.

(EA 65346. All © Trustees of the British Museum)

I hope this example gives some idea of what RTI can do to aid research of material surfaces. The aspect of RTI that I cannot show here on the blog (yet...) is the ability to reposition the light virtually. This re-lighting feature together with the different rendering modes constitute a powerful toolkit for studying the details of material surfaces, whether one is a conservator, art historian, text scholar, archaeologist or even...undertaking criminal forensic investigation!!

Thursday, 8 March 2012

As If By Magic!

TOPOI House, from where I write this post
The interdisciplinary environment created by the COFUND programme here at Freie Universitat is something I am quite excited about. To be able to work at the intersection of the Excellence Cluster TOPOI and the Institute for Ancient Near Eastern Studies, as well as the Egyptology Department presents opportunities for taking my research on early writing and art in new directions.

Given that this is the first year of the COFUND fellowships, the procedures and infrastructure to support such interdisciplinary work are undergoing refinement. With the help and advice of excellent staff in the collaborating departments, we have been figuring out how to get my research funding administered. When establishing new networks, a period of settling in simply comes with the territory, so my recounting this is by no means a criticism. In fact, having been based in the UK HE system for years, seeing how the German system operates is super valuable. I need to learn what is required when bringing together different project partners in this academic environment since one of my goals is--by the end of the fellowship in May 2013--to have developed and achieved funding for a follow-on project involving RTI (...fingers and toes crossed!).

So, beyond literature survey and a bit of writing, the past couple of days have been dedicated to ensuring I can finish assembling my RTI gear and fund research and conference travel. Then I can set about organising my museum visits in earnest to the Louvre, UCL Petrie Museum of Egyptian Archaeology, British Museum, Ashmolean Museum, the Berlin Museums of course--and all being well with the events in Egypt--the Egyptian Museum in Cairo.

During each museum visit I will be doing RTI on about a dozen objects. The type of RTI I will do is called 'Highlight RTI' or H-RTI--and as I'll explain in my next post, is quite versatile since it does not require a lighting dome. Here is an example of some of the H-RTI kit I will shortly be ordering in for my COFUND project.

This equipment belongs to the University of Oxford who kindly lent it for my H-RTI fieldwork at Qubbet el-Hawa, Aswan with the University of Jaen this past Jan-Feb. Oh look...Antonia, our little Abyssinian kitteh thinks she can haz RTI too!

H-RTI in action at Qubbet el-Hawa in the magnificent Middle Kingdom tomb of Sarenput II. Here I am taking some 50 photographs, while applying the flash in different positions, of the decorated rim of a ceramic New Kingdom jar found in a neighbouring tomb last year. Sarenput II's tomb provided an excellent 'lab' space this kind of work--much to his objection I'm sure! For a virtual tour of his grand tomb, check out the 360° view for Tomb 31). 

With a high quality camera, hand-held flash and various other small gizmos, plus a laptop, these together will constitute my mobile laboratory for data capture, image processing and analysis. H-RTI might look like conventional digital photography in many respects, but there is a neat twist that I will explain in due course for readers not familiar with this technique. In a nut shell, careful manipulation of shadow and light can make the invisible visible! David Blaine (or equally Copperfield) -- eat your heart(s) out!

Monday, 5 March 2012

Past the First Post

So here it is: my first post on my first blog! A blog about the past--but also about the present, and by the time of this blog's conclusion 15 months from now, something of the future.

I've just begun a COFUND Research Fellowship with the Dahlem Research School, in affiliation with Excellence Cluster TOPOI and the Institut für Altorientalistik at Freie Universität Berlin. From now until May 2013 I will be undertaking a research project on some of the world's earliest writing and other imagery from ancient Egypt and Mesopotamia. Exciting stuff - if you're in to this sort of thing! 

My project is entitled: ‘A Comparative Study of Scribal and Artistic Spaces in Early Egypt and the Ancient Near East: Integrating micro- and macro-scale analyses’. I'll explain more about this in future posts -- about 3 times per week. In addition to a spot of field work in Egypt, I'll be poking around museum basements (love museum archaeology!) as I collect my data, including photographs of hieroglyph-inscribed funerary stelae, seal impressions, cuneiform tablets, decorated vessels, etc. 

A key topic on this blog will be the open access digital imaging technology, Reflectance Transformation Imaging(RTI). This is a method of photography which enables the virtual re-lighting of material surfaces and will be a tremendous aid as I research early scribal and artistic use of materials, tools and techniques. I've been using RTI for a while, but the RTI community is growing quickly and new developments in hardware and software are continually emerging. So I will also be posting my general thoughts and views on RTI news and developments.

Well, I've managed to polish off an Eidauer Schwarzbier in the writing - aroma of caramel and roasted malt, not too sweet. A fine blogging companion.