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 moving...it'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!

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!!