How to photograph a coin so software can read it

Coin identification is a reading problem before it is a valuation problem. Almost every scan that fails, fails because the photograph did not contain the information: the date was in shadow, the mint mark was a blur, the coin was at an angle that squashed the legend into an ellipse.

Five habits fix most of it.

1. Get the coin flat and parallel

Lay the coin on a surface and hold the phone directly above it, not at an angle. A tilted shot foreshortens the legend and turns round letters into ovals, which is exactly the kind of distortion that turns a 3 into an 8.

2. Fill the frame

The coin should take up most of the picture. A coin sitting small in the middle of a kitchen table gives the reader a few hundred pixels of actual coin to work with, and the mint mark is a single letter roughly a millimetre wide on the real object.

3. Diffuse the light, and put it to the side

Direct overhead light does the worst possible thing: it blows out the flat fields and leaves the raised design without a shadow, so the relief disappears. What you want is light coming from one side at a low angle, softened. Near a window on an overcast day is close to ideal. A lamp with a sheet of paper in front of it works too.

Flash is usually a mistake on a shiny coin. It reflects straight back and burns out whatever it hits.

4. Use a plain background

A dark, matte, plain surface. Not a wood grain, not a patterned tablecloth, not a newspaper. The reader has to find the edge of the coin before it can do anything else, and a busy background makes that harder for no benefit.

5. Shoot both sides

The obverse usually carries the date and the portrait; the reverse usually carries the denomination and, on US coins, the mint mark. Either one alone can be ambiguous. Both together almost never are.

Buck counts a front and a back of the same coin as one coin, not two, so there is no cost to flipping it over.

What to do about a coin you cannot read

If the date has genuinely worn away, no photograph will bring it back, and no honest tool will invent it. What is left is identification by type: the design, the metal, the diameter. That is often enough to name the coin and give a wide band, and a wide band is the correct answer to a coin that does not have a legible date.

Do not clean it to make the date come back. Cleaning removes the surface, the surface is where most of a collectible coin's value lives, and the damage is permanent and obvious to anybody who might have bought it.