Numismatic and History Discussions > Coin Photography, Conservation and Storage

Article of Interest/Imaging of Coins

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museumguy:
Hi All,

Discovered (sort of by accident) this interesting article on coin imaging.  Its long and a bit technical for my small brain but there appears to be a lot of interesting stuff regarding new methods of viewing coins (focus on ancients) using Reflection Transformation Imaging - sort of a virtual look at coins.  Check it out.  I've got to spend some more time with it myself.

Steve

http://www.c-h-i.org/events/VAST2005_final.pdf

Gilgamesh:
 ;D Thanks for the link. I'm about to start trying this.

moonmoth:
Well, it is interesting, but you need a lot of resource to do it.  Their original subject, a cuneiform tablet, required 400 separate photographs.  Luckily, the paper describes a method for coins that only requires 48 photographs per coin.

You also need a purpose-built stage, special software to integrate the photographs, and special software to view the result.

You would have to be really serious about remotely studying a coin to do this.

bruce61813:
If you look up "photogrammetry" you will find there is software that is capable of doing this type of work. It has been around for over 20 years, and started with special calibrated cameras. then progressed into the digital world as equipment became better. Look at this site: http://www.photomodeler.com/index.htm.

 there used o be a simple program available that allowed to to photograph and object, then by marking reference points, the computer would use the 2D images to create a 3D picture, they could be rotated, turned or twisted in any direction.  the total detail was only limited by the number of pictures us used. for a normal item, say a child's block, 6 pictures worked, one of each face.  A vase required more , about 12 plus top and bottom. The more the easier it was for the computer to reconstruct the image. the 'operator' did have to supply 'key' point markers for alignment purposes. I think the software is still on the web somewhere. If I also remember correctly, the 'output' included the controls for viewing.

Bruce

cdschroer:

I'm one of the authors of this paper, and ran across your posts.  I thought folks might be interested in our website where you can see more coin examples that use the technique and can be interactively viewed with different lighting.

http://www.c-h-i.org/examples/ptm/ptm.html is the index page, and there is a coin gallery available. You need a Java enabled browser to look at them.  The demos are low resolution due to web constraints, but we shoot at a much higher resolution, that allows you to zoom in and out.

You can also learn more about this technique, in a less academic format, from this article on our website:  http://www.c-h-i.org/technology/ptm/ptm.html

This technique is quite different from photogrammetry (something we also use) in that it generates 3D information  based on the reflectance properties of the surface, and stores it in a 2D format. This surface information allows you to see fine detail of the surface characteristics, more than you would get from a 3D model, and with enhancements, more than you can see on the object itself.  Also the technique works on highly reflective material, which is very difficult to capture with traditional 3D scanning and imaging techniques. The article I mention has a good explanation of what's going on for those who are interested. The technique has been used to decipher heavily worn and/or corroded inscriptions, most famously on the Greek Antikythera mechanism. http://www.hpl.hp.com/research/ptm/antikythera_mechanism/index.html

And finally, there is a new technique for capturing this type of image that we developed last year in conjunction with HP labs that doesn't require a light dome. So, it's easy to try out without investing a lot, and it's more flexible for different size objects.  We've been using it for documenting rock art.

We are a 501(c)(3) non-profit corporation, and the software we develop will be made available as open source.  We have some active projects and expect to make more stuff available during 2008.

Thanks for your interest!
Carla

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