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This blog is a brief intro to RTI (Reflectance Transformation Imaging) and my personal tips and tricks. You find everything on the website of the group developing the tool.
I must say I was not that excited the first time I heard about it while I was fellow in conservation science at the Metropolitan Museum in NY in 2010. There was an RTI training section and yes, I thought it was a kind of enhanced-raking light-Photoshop method. Though, after testing it myself, I have been captured by the fact that it produces an actually useful documentation with basic equipment and pretty fast and simple procedure. I find RTI especially useful for my work in support for appraisal and authentication professionals. When you want to share the “feeling” of the painting’s surface with the team you are working with – but they are scattered around the world and you are the only one who has access to see the painting.
What you need. I have to do Reflectance Transformation Imaging – RTI – all alone with as a light equipment as I can. So this is what I figured out.
- Camera. I recommend an high-resolution camera. Since stitching photos to get bigger images is not an option here (you should do the same stitching at least 24 times!!) you should use a camera with pixel count enough to get the details you need. I use my beloved Nikon D800, 36 MP.
- Black Spheres. You can be creative and try to experiment using everything you find suitable. I have used black marbles (this were pretty awesome), ping-pong ball painted black, mini billiard number 8 ball (it is already black and you find it on eBay sold as a key chain) and ball bearings.
- Lighting. I prefer halogen spotlights, IKEA mainly. I always avoid using Flash light to document art. Their CRI – color rendering index – is pretty low.
- Software. Manuals and software on the RTI group’s website.
- Metering tool. You need to put the lamp at the same distance while you move it around the object and at different angles. I use Bosh DLE 40 laser rangefinder. It’s precise (1.5 mm), small and lightweight. It fits perfectly in one hand.
- Remote shutter. As i said I work alone. don’t get me wrong. I’d love company but that would dramatically increase traveling cost and so on.
Let’s start! This video briefly describe the hardware and software process. It’s just a brief description all the details you need to know are on the CHI group website.
Infrared RTI. Yes, you read right. I did some Infrared RTI. It has some advantages. When it comes to infrared reflected, the better contrast to read the underdrawing can be achieved at different lighting angle for different areas. So, for example bright areas have a different behavior than dark areas. See the shots below from an Infrared RTI I did on a mock-up painting with a underdrawing squaring grid. More details about this painting can be found here. It result that on bright areas the underdrawing grids are better visible in raking light while in the darker areas they are better seen in top lighting. Compared with the normal digital infrared image, it seems, Infrared RTI can give a better imaging of the underdrawing.
Infrared Reflectance Transformation Imaging. lighting from bottom left. Infrared Reflectance Transformation Imaging. Lighting from top left. Infrared Reflectance Transformation Imaging. Lighting from middle right. Infrared Reflectance Transformation Imaging. Lighting from center. Infrared Reflectance Transformation Imaging. Lighting from top left.
Thanks Antonio. We hope to try RTI on a Greek pot. Have you ever worked on objects with it? And can you please credit your musical background? I Solisti Veneti perhaps?
Hi Susan, thanks for your appreciation of my blog! I’m actually doing RTI only on paintings but you should not any problems on 3D objects. I would just try to have as much depth of field as possible, closing aperture a couple of stops from the smallest (to avoid diffraction). And use lots of lighting. Then it depends if you want document just a small (almost flat detail) or all the crater.
Music credit is: Advent_Chamber_Orchestra, Handel, Entrance_to_the_Queen_of_Sheba_for_Two_Oboes_Strings_and_Continuo_allegro. For my videos I find inspiration using and browsing free music from this awesome site freemusicarchive.org Ciao Susan!
RTI on 3D objects like pots, Cuneiform tablets, etc is, possibly, even more impressive than in paintings. The ability to infinitely relight the object from endless angles, intensities and filters, really brings out the 3D information.
Like Antonio says, it is essential to controll depth of field. Closing down the aperture is essential. Obviously, the smaller the object, the closer the distance. The closer the distance, the smaller the depth of field. A very sturdy tripod too is essential.
Here is a link to a few examples of my work:
http://www.zupdom.com/moshecaine/research/research_rti/rti.html
If you intend to shoot many small pottery objects I would highly suggest constructing an RTI dome. You can find lots of info on the topic online.
I’m very glad this blog is becoming an active forum to share useful tips and tricks among professionals of different backgrounds!
Antonio. I have also done some experimentation on combined RTI and infrared, on some fragments of the Dead Sea Scrolls, together with a colleague of mine, Michael Magen, head of paper conservation at the Israel Museum. Due however to the sensitivity, both of the actual fragments and no less to the highly explosive topic, we were not able to full complete the investigative process. The results, however, we’re very encouraging. The IR enabled to clearly view the texts hidden beneath the dark encrusted top layer, while the RTI enabled to clearly examine the surface of the parchment.
Here is a video of a similar experiment carried out on an illuminated manuscript at the museum.
http://www.zupdom.com/moshecaine/research/research_rti/research_rti/hagaddah.html
I also could appreciate on your website your portfolio of artistic photography!
We have also done some micro RTI work, using a Dinolite as our imaging source.
For a micro black ball we used a ball fom a ball point pen, painted black.
The light source was a small LED penlight torch.
It works!
I admit I would have never thought of a pen ball for the micro RTI, excellent idea!
Hi, everyone. I’ve just discovered this technique on the web.So far, I haven’t gone beyond exploring the software and transforming some sample images, but I’m impressed! I’ll be using the technique for exploring surfaces of materials, and I hope to include some images. in the very near future. Best wishes, John Anderson, Ireland.
Hi, again. I’ve had good results with a variety of test subjects, but have a question. I capture my stack with a hi-res camera (Canon 5D2) and Zeiss macro lens. I convert RAW to DNG/TIFF. So far, I have high-resolution images. Then, peversely, I have to convert my high-res images to JPEGS, losing most if not all image high-freqency detail in the process!
What is going on?
Why not simply use DNG files and preserve detail? I can’t ask this question of CHI because their ‘forum’ won’t allow me to register. Anyone?
Kind regards,
John Anderson.
Hi john,
hope somebody at CHI see your comment. though, I guess it would be a bit too much for a PC to handle big DNG files in order to make the RTI file.
Thanks, Antonio. It’s a pity, because jpeg compression causes considerable loss of fine detail and, after all, PCs are becoming faster and cheaper every year!
Kind regards,
John Anderson.
Well, let me know if you get any answer about it. I just had to buy a new PC. My just 1-year old PC was not enough for the imaging I’m doing now.
Thanks, Antonio, I did receive a reply. There are no plans to extend capture to hi-res images. Great pity.
We are using a Dell workstation to process RTIs. We’ve installed 128GB RAM; that, and fast dual-Zeon processors runs through a 40-image jpeg stack (dumbed down from Canon 5D2 RAW files) in under 60-seconds. Just enough time to pour a coffee!
I’ll post some of our forensic RTI images soon on Flickr.
Regards,
John.
I actually read that reply since I was on the RTI forum to post my own question. How to run RTI viewer and builder on Windows 8?? I just switched to this operative system and they don’t work. 120 GB Ram..wel you definitively have much more computational power! I just switched from 8GB to 16 GB and I thought it was a great improvement! But 120GB, that’s a lot… ahah
Hi, Antonio. It’s well worth the expense of populating your PC with as much RAM as possible. (It’s inexpensive these days). Otherwise the CPU will use the hard disk, and that quickly slows down computations. In addition, two hard drives should be fitted (again, cheap); one for program storage, the other a scratch disk to hold your images. It makes all the difference! By the way, you didn’t say what make of PC you bought? As for Windows 8……
Regard,
John.
Antonio, You say RTI won’t run on your Windows 8 platform. RTI is written in the high-level Java language, and should run on most machines with JAVA 6 or later installed. As for Windows 8, it is an unmitigated disaster, far worse than Millenium or Vista. Microsoft no longer seem to care about professional users; I suspect Windows 8 is designed for idiots!
However, there may be a compatibility mode available, which allows you to run software designed for windows XP/7. Alternatively, if you can find a techie with an OEM XP disk, he can reformat the drive and load that instead.
Let me know how you get on.
Regards,
John.
Hi John, thank you so much for your hints on Win8. I should have heard from you before I did switch to Win 8!!! Anyway, unexpectedly I manage to get the builder working just by re-installing the Java machine. But still the Viewer shows a flat red screen in the RTI window. I posted about this problem to the RTI forum, I’ll see what they’ll say. This is a problem other unlucky Win 8 users are going to have.
John, let me know if you publish anything of your RTI works. I am really interested to see. For the little I understand you work in a forensic company? I’ll be interested to know other applications of RTI in forensic that would match art examination. I used RTI for documenting signs and incisions in the ground.
Hi Antonio, go to the link I posted, you may find the fix works; otherwise, you’ll have to try and find someone (are you in the ‘States or in Europe?) to install windows XP Pro for you. It isn’t that difficult – I’m aware of many professional users in Britain, and here in Ireland, who are experiencing major problems with Windows 8, and are reinstalling XP or 7. Microsoft sucks.
I’m a materials scientist and principal of a small company carrying out a variety of investigations on polymers, documents, wood, etc. for the legal and insurance professions. Much of our our work involves chemical and instrumental analysis. We’re currently still evaluating RTI (but curse the jpeg-only format!) I’ll be posting the results of our endeavours as soon as possible.
Let me know how you get on.
Kind regards,
John
Now you’ve reminded me, I must send a donation to CHI.
Hi John , thanks again for your tips. I can install Win 7, no problem. I’m in Italy now, running my start up technical art examination service. let me know when you post something. Ciao
Antonio, try this:
http://lifehacker.com/5965889/how-to-run-windows-xp-for-free-in-windows-8
Regards,
John.
Hi, Antonio, sorry for the delay posting RTI images to Flickr. There are major problems currently with that site. Yahoo say they’re fixing it. As soon as I can post I’ll let you know.
I’m pleased to hear you resolved your PC problem by reinstalling Win 7. Interestingly, there is so much anger at Microsoft’s Win 8 rubbish, DELL are offering WIN 7 as an alternative OS for their machines.
Best wishes, John Anderson.
Hi John, thanks again for your hints!
Hello Antonio. My colleague Tony Kavanagh (he’s the Flickr expert) has kindly set up a Flickr group called Forensic RTI Imaging. The web address is
http://www.flickr.com/groups/2167393@N20/
We’ve started by posting a humerous image. Do you think you could carry that around with you!
Please feel free to post images and discussions. We’ll be posting more (serious stuff!) in early course.
Kind regards,
John.
Hi John, i just signed to the group. Yeah, that’s the largest RTI sphere ever!! ahaha
On Sun, Mar 17, 2013 at 5:29 PM, Cultural Heritage Science Open Source
Hi. I am working on a master’s degree in Art-history. Especially i am interested in restoration of artifacts through the RTI method. It is so imformative to me 🙂
i am conservator i would use Reflectance Transformation Imaging (RTI) System for carbonized papyri
could you provide me some tips and tricks IR-RTI
thank
Hi Mohamed,
sure, I’m happy to help you. What you need to know specifically? have you done RTI already?
hello Antonio, Ive read what u have achieved ,, its really a great job , i appreciate what u have reached and I would like to ask if u have did RTI with UV Reflection !!
Hi Ayman,
thanks for your appreciation. I didn’t do RTI with UV radiation but I recall some other professionals did and used it for detecting incisions in transparent materials such as glass and crystals.
buenas tardes Antonio, recien me esoy iniciando el el tema, sono una duda me instale el programa y cuando termino de procesar me sale error Pach HSH
Hi Albert, the issue could be due to a number of facts. Try to install on a different computer with another operative system.
Dear Antonino,
First of all congrats for this great endeavour. It is really important that you mention an alternate option instead of buying the much expensive RTI equipment. To that end, could you please a be little bit more specific about the equipment that you used? I am quite new in this technique which I am intended to use in recording rock art.
So, what equipment did you exactly used?
With thanks,
Panos
Hi Panos, thanks for the appreciation of the blog and this post. My recommendation about RTI is just to try try and try it as much you can. The method itself is pretty simple and can be implemented in thousands of ways. so, try to start with the equipment you have already and move from there to improve your workflow, if necessary. you just need any camera, a black sphere, and a light. That’s all!
Thanks for the tip. I would also like to ask you if it can work in open air sites with bright sunlight. If not, should then be performed during the dusk? What do you think?
Hello Mr. Cosentino,
I found your site about the RTI method and I really like how you explain it all there. Your video is also absolutely great! 🙂
Some time ago we started experimenting with the RTI method. We want to try to digitize coins and seals.
Unfortunately, We are still at the beginning. We installed RTI Builder on Windows 10 and Mac OS. But we can’t load images anywhere. We have a correctly named jpg_exports folder. But either the image loading crashes or nothing happens. We use JPG images.
We’re running out of ideas on where we are making mistakes. Could I please ask you for advice?
Klára