Sometimes you find yourself confronted with the limitations of macro photography. Even at a very high aperture, your depth of field can be extremely limited. So what can you do when you want to photograph something that’s very high relief, or something at different angles that show alternate dimensions of a coin?
Luckily image editing programs can do wonderful things these days, and the technique known as "Focus Stacking" can yield some surprising results. There are different programs that you can use, but for the purposes of this demonstration I’ll be using Adobe Photoshop. It, of course, is the gold standard of image editing, and Adobe’s Creative Cloud subscription service makes the program quite affordable.
The gist of focus stacking is that you take several exposures of an object, focusing on different parts of that object with each exposure. Let’s take the example of one of Bruce Morelan’s fabulous dollars: The 1802/1 MS64 Col. Green-Newman piece slabbed by PCGS.
Firstly, it’s important to keep the camera as stationary as possible. So use your copy stand or a heavy-duty tripod to keep it stable. This was done with a tripod. Once you have your lighting set up, snap away. Seven exposures were taken of this slab. Even at ƒ11 the depth of field is quite small.
Once you’ve photographed all that you want in focus, now the fun begins in Photoshop.
Go to File>Automate>Photomerge.
This is a tool to allow you to combine images in a number of different ways, and is quite effective at assembling panoramic photos. I recently assembled a panorama that I had printed at 82" x 9", but that’s another story.
Once you’re in the Photomerge dialog box, make sure the Layout selection is checked on Auto (it should be by default). Browse and select all of your files you wish to merge. Make sure that the "Blend Images Together" box is NOT checked.
After clicking OK the computer will start working. What it’s doing is automatically aligning all the images together.
The end result is a layered image. Select or highlight ALL the layers you wish to merge. Then go to Edit>Auto-Blend Layers...
Once you do that another dialog box will open. Make sure the blend selection is set to Stack Images, and you may or may not need to also select the Seamless Tones and Colors box. I’ve always checked it for good measure.
The computer will then start working again to create layer masks for each layer, in order to display every element that the software can detect is in focus in the image. It’s not 100% foolproof, and may require additional editing, but the end result can create images that are very nearly completely in focus.
There are many coins you can try this out with, but one of the ones I was particularly itching to (safely, and very carefully) experiment on is the St Gaudens High Relief Double Eagle. Even using this technique, nothing can ever really show how three-dimensional this coin is. But at this very steep angle, you can see a little bit more of how the dies were engraved. Each of these shots needed about 8 exposures each. Shown is one shot of the component images, followed by the completed merged image.
There are some limitations that I’ve noticed with this technique. Sometimes that gap between what’s in focus and what isn’t can be too large for the logic of the software to seamlessly put together if objects are relatively far apart. One example is a very, very, very high relief Napoleonic medal I came across. The edge of Napoleon’s hat is just massive, and my attempts to have the name "Bonaparte" in focus, which is visually much more distant, weren’t successful. But that’s OK. Having "Bonaparte" out of focus just makes the relief of the hat pop out more.
Four exposures were made of the Napoleon focus stack. Shown below is the first exposure with the face in focus, and the last with the tip of the hat in focus.
I hope this little tutorial will help you see your coins from a slightly different perspective. Happy shooting!