Bob Van Arsdell submitted these thoughts inspired by Wayne Sayles' article excerpted in last week's issue. Thanks!
I enjoyed Wayne Sayles' numismatic sleuth work regarding the coin found in Israel. That coin is likely flat and in low relief. Thus, there probably isn't much to question in his work.
But it would be a pity if the techniques were applied willy-nilly to photographs of other kinds of numismatic objects. Many coins simply aren't flat – the Byzantine scyphate series would be an example familiar to many readers. While it may seem that flatness shouldn't be a big deal, in practice it is.
Wayne has more experience than I, but I have photographed hundreds of Ancient British coins and processed thousands of images in Photoshop. These Celtic coins are seldom flat, and they simply don't photograph "right". When you place the coin convex side up, the coin sits on its rim. Thus the plane of the rim and the plane of the camera are parallel – if you set the camera up correctly. When you flip the coin over, it lands on the convex side, and flops over until it makes its peace with gravity. Now the two planes are not parallel. The effect is the same as shooting the coin from an angle. In this case, the two photos will not have the same shape. A similar affect could occur whenever a coin has appreciable relief.
Sure, the photographer could orient the coin on a "bed of sand" to eliminate the problem. But no one has the time to do it, especially if hundreds of coins need to be photographed quickly.
Photoshop processing creates its own set of problems. Coin photos usually appear with nice white surrounds, as if the coin was photographed floating in space. The fact is, someone has erased the background. Though Photoshop has amazing tools for doing this, they often don't work well on coins. The shiny metal surface fools the Photoshop algorithms, and they fail to find the edge of the coin accurately. Usually, the Photoshop worker gives up, and simply uses the eraser tool to "carve out" the coin. This manual process can result in different carves for the obverse and reverse – again made worse by the level of workload.
Often, "setting the camera up correctly" isn't possible. How many coin illustrations start as iPhone shots, grabbed hand-held at a coin show? There is no reason to presuppose the camera was set up right unless you know how the coin was actually shot.
Some coins fail to cooperate at all. Try photographing a cast coin with "cold shuts", where the metal has frozen before the mould is filled. The coin will have little holes in it, but they may not be straight-through ones. Photograph it on a white background, with the light streaming through, and the hole shows up as a nice white spot. Flip the coin over and the light no longer goes straight through, and the hole disappears.
Why all this photographic pedantry? It could save writers embarrassment if they didn't jump to conclusions. Many years ago, I published an article about a strange example of a gold Stater. It was struck from late state-dies on a flan made from very debased gold (unlike the normal examples). Almost immediately, another writer complained that I simply had it wrong – that the coin was just a plated example, with a copper core. A few years afterwards, at a conference, someone stood up during my presentation and shouted that the coin was just an ancient cast forgery. After a bit of to and fro, I had to shut discussion down with "I own the coin – it's not cast!" It wasn't a plated example, either.
What I suspected, is that neither of the two commentators had ever seen the coin. It had left the UK years before either of them would have been interested enough to track it down. They had only been looking at photographs, and couldn't possibly have seen the details necessary to arrive at a sensible interpretation.
My warning to would-be authors is: SOMETIMES YOU HAVE TO SEE THE COIN.
To read the earlier E-Sylum article, see:
PHOTO SLEUTH SAYLES QUESTIONS COIN FIND REPORT
Wayne Homren, Editor
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