On the 1st February the OuRTI team went up to Winchester Cathedral to help run an RTI workshop. The cathedral contains a range of highly important memorial inscriptions and is also home to a huge collection of graffiti spanning several hundred years. The event, organised by James Miles from the Archaeological Computing Research Group, aimed to help researchers and tour guides at Winchester Cathedral to use computational photography to document and to better understand these inscriptions.
The day was a huge success and attracted a wide range of participants. Many brought their own cameras and equipment and left with the skills to produce their own RTIs. The event was a valuable opportunity for us to continue to develop techniques which we have been using in our work with the Churches Conservation Trust. Particularly interesting was the recording of ledgerstones, memorial stones which are placed into the floor of the church. The instriptions on these stones are frequently highly eroded and consequently RTI is a very useful technique which can help us to read inscriptions which are undocumented and which have been unreadable for many years.
Next week, from the 16th to the 20th July, the Re-reading the British Memorial project team will be in Holcombe, Somerset, working with Wessex Archaeology, the Churches Conservation Trust, Somerset Archaeological and Natural History Society, Somerset County Council.
We will be supporting a series of activities taking place at St Andrew’s Church, Holcombe, Somerset, as part of the Festival of British Archaeology.
Over the course of the week, there will be a number of technology driven experience/training/demonstration sessions in archaeological survey (GNSS/TST), RTI, laser scanning, aerial survey (using UAVs), geophysics plus some great guest talks/lectures. Some of the events are bookable and early booking is advisable due to limited places.
We will be running RTI workshops at 1pm on each day. You can read more about our workshops, and access a booking form here: http://www.wessexarch.co.uk/85880/reflectance-transformation-imaging
We’re very excited to be working with such a cool project, and to be participating in the Festival of British Archaeology. Please do come along if you’re in the area, we’d love to see you there!
See the Wessex Archaeology website for more information: http://www.wessexarch.co.uk/85880/st-andrews-church-holcombe-somerset
St Andrew’s church is located just off the Fosseway to the south of Midsomer Norton:
Some useful links relating to the event:
Festival of British Archaeology: http://festival.britarch.ac.uk/
Wessex Archaeology: http://www.wessexarch.co.uk
Churches Conservation Trust: http://www.visitchurches.org.uk/
Somerset Archaeological and Natural History Society: http://www.sanhs.org/
Somerset County Council Heritage and Libraries Service: http://www.somerset.gov.uk/irj/public/services/directory/service?rid=/guid/b098cddb-0437-2c10-d999-bcb382eb1617
Archaeological Computing Research Group, University of Southampton: http://acrg.soton.ac.uk/
The team here are very excited as we are putting plans in place to host a free workshop for all interested organisations and groups to come and visit the University of Southampton and try out some of the low-cost and free technologies that we’ve been testing with our project partners.
The workshop date has yet to be confirmed, but we are anticipating that it will be held in August-September 2012.
If this is something that you would be interested in attending, please register your interest through our eventbrite page below so that we can get an idea of numbers of attendees and keep you up to date with developments:
Visiting Royal Garrison Church
Last week, Gareth, Adam and I travelled to Portsmouth to work with the team there on recording some very challenging memorials.
The Royal Garrison Church in old Portsmouth, maintained by English Heritage and a dedicated team of volunteers has an impressive situation. Nestled behind the sea defensives and located near to the historical dockyards and harbour front of the old city of Portsmouth, the church was built in the thirteenth century. The church was badly damaged during World War II, and so the nave has no roof. The chancel is beautifully maintained and has some gorgeous oak stalls from the late 1800s, and I am looking forward to going back there soon to read the memorials there dedicated to famous sailors.
As you can see from this photo that Adam took in the morning, the church has part of its roof missing, which means that the memorials are very badly eroded. Text that was legible a mere ten years ago has today eroded away to almost nothing.
A member of the team at the church contacted us following the presentation that we gave at the South by South West Creative Digifest event in May, and asked if we would be interested in trying out RTI on some of the more problematic memorials at the church.
Below is an example of the state of the memorials. Although very well cared for, the proximity of the sea has been taking its toll on many of the memorials fixed to the wall in the uncovered part of the church.
There is lots of information about the church on the Memorials and Monuments in Portsmouth website, including a very comprehensive list of transcribed stones. So we had some great data to work from when we started.
In the morning we met with some of the Royal Garrison team members and gave a demonstration of the RTI method, showing some of the files that we had made at previous sites. Then we went to the roofless part of the church and identified the memorials that were the most erroded, and for which the team had not yet managed to get a full transcription from.
Recording the RTIs
We had no idea how the RTIs would turn out, so this was an exciting one for us to do. RTI can only show us what already exists, and in this instance, it was very hard for us to guess at what might remain of the transcriptions.
In the photo below you can maybe get an idea of the situation of the memorials. They are mounted on a wall, quite high up, and each memorial is flanked on either side by columns.
The columns to either side of the memorials proved to indeed be problematic as it meant that we were unable to record some portions of the object. I’ve drawn a quick diagram to illustrate what I mean:
We went back to the University after our visit and ran the photos that we had taken through the software to see the results. Our fears were confirmed, most of the ghost remains of the letters from the memorials were indeed almost totally eroded away.
However, the RTIs did give us more information than we had been able to get with the naked eye. I’m going to put together some nice screenshots of the RTIs for you to see, and will write another post on them next week.
As always, we are very grateful to the team at Royal Garrison Church for being so hospitable (and for the much-appreciated cups of tea!), and look forward to returning soon to record some more of the memorials. I’ve included some images below so that you can get an idea of some of the challenges ahead:
I have been spending quite a lot of time lately working with Reflectance Transformation Imaging (RTI). It is a computational photography technique developed by Tom Malzbender at HP labs. It is based upon photographing an object from a fixed camera position, in each image the lightsource is moved. These images are then compiled into an interactive image within which the light can be virtually moved. As well as light movement the RTI allows the user to control a range other other variables and to render the surface using a range of algorithms which alter the surface appearance of the objects in the scene. In archaeology this technique has great potential as a means of dissemination (this beats a normal photo) but also as a means of interpreting things which are not normally visible to the naked eye. It is this technology which first inspired our (Nicole and I) project, Re-Reading the British Memorial. Much more can be found on the website of Mark Mudge and Carla Schroer’s organisation Cultural Heritage Imaging. They have popularised this technique for cultural heritage in the USA and have created an abundance of materials and advice all available at no cost. Amazing.
One of the things which makes RTI capture so fantastic is that you need very little equipment to get recording. As if to prove this point, Graeme noticed this morning that the IOS 5 version of the interface for the iPhone has a focus and exposure lock. This means that the iPhone camera can capture RTIs! Here is how we did it, with preliminary results.
So the first challenge was to attach the phone to a tripod, this was easily solved with a few elastic bands. Next and perhaps most challengingly we had to figure out how to adjust the exposure control so that the vast majority of the light in our images came from our mobile light source instead of the ambient light in the room. There are no explicit settings for this on the iPhone so you need to trick it. We put the light source right by the object we were capturing to slightly over-expose the image. We waited for the autofocus to adjust to the high light levels, then I turned the autofocus/exposure lock on by holding my finger on the screen for a few seconds. When you take the light source away you have a totally dark image which becomes beautifully exposed when your light is switched on. Perfect.
Next, you capture as normal. We had no way of triggering a flash from the iPhone so we used a constant light source (a deconstructed desk lamp). We didn’t have a remote control either so we had to just very gently tap the shoot button and hope that the camera didn’t move. The highly sensitive controls on the iphone made this possible but I have noticed that a remote control is available so probably is worth the investment. In this case we were lucky and the camera didn’t move.
The result was extremely impressive, the iPhone camera is only three megapixels so this is not the highest resolution option but it certainly has the power to reveal things which are invisible to the naked eye. More importantly it places the technology needed to make RTIs into the hands of anybody with an iPhone a desk lamp and a reflective sphere.
I am sure this is possible with other mobile devices too. Get your phone out and have a look!
Lit from the front:
I have added this post to my own blog also: http://gcbeale.tumblr.com/post/22316986752/iphone-rti Here I write mostly about my own research into Roman painted statues and digital representation, so take a look there if you are interested in following this work.
We’ve been looking into how RTIs can be best shown through the web.
In the same way that a video needs to be opened inside a video player, to view an RTI as an interactive experience, an RTI viewer is usually installed onto the computer of the person who wishes to open the file. But there are some great web-based options being developed that will allow users to view RTI files within their internet browser. There is one that Hembo Pagi has made that allows for viewing RTIs within a WordPress blog, and we are certain that more versions will be developed.
For now, we have recorded a video of Gareth using an RTI viewer on his own PC, so that you can see what kind of thing you can expect from an RTI.
This is a gravestone that we recorded whilst visiting St. George’s Church on Portland.
Halfway through the video (go straight to about 37 seconds for the best bit), you will see that Gareth zooms in on part of the inscription, and switches on an option for ‘specular enhancement’, and this is where the real magic happens. All of the text inscribed on the stone suddenly becomes visible, and easily readable. This is exactly the sort of result that we think will contribute to interpretation of problematic gravestones.