----------     Photographing Ancient Coins     ----------

Coin Photography – Processing Your Image

There are ten pages about photographing coins:

eeping Detail in the Highlights

Once you start playing with your image in Photoshop, you will find that it is very easy to lose detail in both the highlights and the darkest areas. The highlights are the trickiest, and with some coins it is easy to end up with a glaring white area on an emperor's head. So I am going to suggest a way to preserve the information you have in those areas, and drop it back onto your adjusted image later. These photos show the technique applied to Securitas on the reverse of a small coin of Constans, with enlargements of the head at each stage. Start with a single, flattened image and do this first:

– Set the colours to default black and white by pressing D.
– Bring white to the top by clicking on the two-headed arrow.
– Select a colour range using select / color range from the menu. This will select the pure white pixels. I use "fuzziness" set to 50.
– Add to that selection by clicking the dropper with the plus sign below it in the selection dialogue box; then go to your image and click on an area that is not quite pure white. You should aim to select only a small part of the image, but definitely more than just pure white. If you get too much, press control-Z to undo that selection and try again.
– Feather your selection using select/feather from the menu. I usually set feather at 5 pixels. (This is the stage shown by photo 1.)
– Now press control-J to ceate a new layer with your selection.
– Make that layer invisible by clicking on the eye in the layers display; go on to work with the original image to make it less dull and more realistic, as shown at photo 2, without worrying about the glaring highlights; and when your work is done ...
– Bring that valuable data right back by clicking the eye again, before you flatten your image for final saving. The de-glared image is shown at photo 3.

This does not work so well with shiny silver coins as it does with bronzes like this one. If you work with JPEGs produced by your camera, then on shiny coins you will usually find some areas which are pure white, containing no data at all. It's still worth trying this technique, becuase you will see some improvement round the borders of those areas, if not perfection. But if your camera lets you work with RAW files, you might find that all the data is still there – cameras tend to lose it when converting to JPEG internally. I should warn you that the technique with RAW files is not so simple, and will vary with your software. I have had some success, but it is easy to end up with very oddly toned images.

evelling and Desaturating

Having taken a photograph of a coin and made the background whatever you want, there will still be a few more steps you might want to take. How far you go with this is entirely up to you. There are those who say that you should not make any more alterations to the image, but in my own view it is useful to bring the image closer to the way the coin actually looks, if that it possible. And, of course, you might want to use the photo as something other than a plain record.

First, you might think that the photo looks a little washed out. The tones in the picture don't cover the whole range from black to white. This can be fixed by tweaking the levels adjustment slightly, bringing in the end markers. Don't take them too far. A little will work better than a lot. You can also use this to lighten or darken the image if you wish, and if one side needs to be lightened more than the other, apply a gradient to the resulting levels layer. If you have combined obverse and reverse into a single image, you might need to adjust levels separately for each, before you merge the layers.

This is better, but in the process of making the picture less washed out, the colours have become artificially overemphasised. The earthy deposit isn't quite that vivid in real life. Adjust this by reducing the saturation slightly. In the example, this has been overdone a little, to show quite clearly what the effect of desaturation looks like. Click on the image to see how it really ended up.

ringing Detail from the Shadows

With a good image to start with, this will be all you need. This is the point at which you should bring back the detail you saved in your highlighted areas, as shown above. In some cases, you might also want to bring out some detail in areas that seem too dark, even black, to the eye. To do this, start with pure black "paint" selected. You might then try adding some of the darkest tones to the selection by using the "color range" dropper labelled +. Only select tones from the very darkest areas if you do this – usually it won't be needed. Then, feather the selection using select / feather. About 5% to 10% of feathering works for me. Then, with image / adjustments / levels, move the right-hand slider over to the left a little; never more than halfway. This will lighten the pixels that have been selected, and leave the rest alone.

If this works well, it will bring out more details of the coin. It can't bring back detail that isn't there at all, though. Be careful to keep the effect subtle. If it doesn't seem very obvious in the example shown, it was very clear what was happening as the slider was moved, and it does make a big difference to the overall effect.

The tweaks on this page should all be applied with care, but this one has a particularly powerful ability to mess up your image by making it look patchy, or alternatively, dull and lifeless. So check out the overall effect carefully before you move on.

harpening - The Devil's Footprint?

When you are happy that the image is right, you can resize the image to whatever size you have standardised on for your coin images. As a last step, my own preference is then to sharpen the image a little using unsharp mask. It's easy to overdo it (as usual), but I find that a small adjustment will compensate for the fact that my camera produces images that are slightly less sharp than real life. Be careful not to make the image unrealistic if it is for academic study purposes or to illustrate a piece for sale. But if the images are for your own enjoyment or for use as art, then clearly this does not apply.

Reducing the size of an image has a sharpening effect, so make it the size you want first. I get good results from Photoshop with "Threshold" set to 3, "Radius" set to 3.8, and "Amount" somewhere between 10 and 30.

There are ten pages about photographing coins: