|by Sebastian Heath|
Scanners and Cameras for Numismatic Imaging
The two most common ways of capturing digital images of coins are to scan them or to use a digital camera. This installment of Numismatics.org will offer a preliminary comparison of these two methods. Figure 1 shows the output from a digital camera alongside that from a scanner. The top two images are of the same 1997 US quarter dollar found in circulation, a.k.a the author’s pocket. The lower two are of an aureus of the Roman emperor Nero issued in 54 AD. The left two images were produced using the Society’s digital camera, the right two using our scanner.
Top: US Quarter; left camera, right scanner. Bottom: Aureus of Nero (ANS 1905.57.29, gift of D. Parish); left camera, right scanner.
In one particular regard this is not a fair contest due to the equipment that was used. The Society’s digital camera is a Nikon D1x, a professoinal grade camera with a current street price of $3,700. The scanner used to produce the images on the right is an Epson Perfection 2450 Photo with a street price of $229. Which is to say that the camera is over 10 times more expensive than the scanner so that one would expect better images from it. I should also say up front that in both cases I have used Photoshop to enhance the images. The intended object of this comparison is the end result as published here in the magazine so that it seemed appropriate to closely model the workflow we use at the ANS.
Looking at the quarter reverse, some immediate points of comparison stand out. When lighting the camera version, I used a single strong light and a high shutter speed. This has the effect of preserving the metallic feeling of the surface but at the cost of revealing all the nicks and scratches on a circulated coin. One has much less control over lighting when using a scanner but the direct light they employ usually bring out the legends on modern coins very well. The camera was clearly superior in revealing the individual feathers on the eagle’s breast, which are largely invisible in the scanned version. The single raking light used in the camera version also means that the lower edge of the coin is almost completely blown out.
The camera version of the aureus is clearly superior. The same single light source was used and in this case the legend of the coin is easy to read. The musculature of Nero’s neck is more subtley represented, as are the details of Agrippina’s dress. Likewise, the camera preserved more detail in the hair of both portraits. Overall, the camera captured a range of shading that is lost in the scanned version. This allows much more detail to be seen.
I don’t present this small case study as a final comparison of the relative benefits of cameras and scanners. For that one would need images of many more coins using a much wider range of equipment. Here at the ANS we have found that there is a lower learning curve with a scanner but that the best results often require careful work with our digital camera.