1908 gold coin

[colohank]

An image of a 1908 Indian Head five-dollar gold coin, shot under axial light. It's one of two $5 gold pieces my father tucked away in a drawer when the United States went off the gold standard in 1933. The Indian-head motif and other details on the coin are in recuse, which means they're incised below the surface of the coin rather than standing above it. I've also attached copies of PowerPoint slides I produced which illustrate a schematic of the setup and of the device I made to facilitate axial-light photography. It's pretty simple. A pane of glass, set at a 45-degree angle, serves as a beam-splitter. Light from the source, in this instance, a single Godox TT685 speedlight with diffuser operating at 1/128th power, reflects off the bottom of the glass to illuminate the subject. That light strikes the subject on the same axis as the axis of the camera lens. Thus, axial lighting. Light from the source which isn't reflected downward to the subject and passes straight through the glass is absorbed by a backstop of rigid, dark, open-cell foam. That prevents extraneous light or ghosts of items beyond which might bounce back, reflect off the top of the glass, and enter the camera lens to degrade the image. A tubular baffle protects the subject from any stray light reflected off the walls of the beam-splitter housing.

The PowerPoint is a for a presentation on higher-magnification photography I prepared for New Dimensions, a continuing education program for senior citizens in Grand Junction, Colorado.

This coin was in general circulation and subject to pocket-wear for twenty-five years before my dad salvaged it. Even though the motif is incised and therefore better protected from wear, I'm amazed by the amount of detail it retains, particularly in the beaded headdress and collar. We certainly don't produce coins of that quality nowadays, at least not coins intended for general circulation.

[Olympusman]

Clever setup.

Mike

[Bob-O-Rama]

Thats a nice fixture and it seems to work great. ( I have a very ugly version of that and it works pretty well, mirror salvaged from a dead digital projector. ) Where did you source the mirror?

[colohank]

It isn't a mirror. It's a 5" X 7" piece of clear glass salvaged from a cheap picture frame I bought at a hobby store specifically for this purpose. Is it optically flat? No. Is it plate glass? I don't know. Would a pixel-peeper therefore find fault with my results? Probably. Do I care? No. What I have seems to work pretty well.

A larger glass might be nice for larger subjects, and I have a thin 10" X 14.5" piece from an older printer/copier/scanner set aside for that purpose. But at four times the size of my current glass, it may be too large and unwieldy.

[iconoclastica]

A great result, with a possibly even greater set up. I'll keep this message in my toolbox, for later use!

[Alex G]

Your results look fantastic! I tried a similar setup for photographing flat soap film (not spherical bubble) which must be lit on-axis or you get no illumination. I ordered a sample beam splitter mirror/teleprompter glass from here: https://telepromptermirror.com/sample/

They charge just $9.99 (or $14.95. Their site seems to list 2 prices! But still... a great deal!) for a 6"x6" sample and you can choose from a range of reflection/transmission values and thicknesses. It's optically flat and designed to be filmed through. I opted for the 50/50 and thinnest available 2mm. It seemed perfectly flat and I had no distortion shooting through it. I did have some issues with ghosting but usually easily solved in Photoshop.

A quick note on your setup - I also placed a black backstop in the same place as your diagram. Even went so far as to paint it with Black 3.0. Something that helped in my setup was to tilt the backstop at a 45 degree angle. This helped me a bit with ghosting. I think some light was getting back to the mirror when I had it pointing flat to the light source. When I angled it at 45 degrees it had the effect of providing the black surface, plus anything that bounced was redirected away from the subject.

Again... very nicely photographed! And wow, what a beautiful coin!

[iconoclastica]

I ordered a sample beam splitter mirror/teleprompter glass from here: https://telepromptermirror.com/sample/
They charge just $9.99

A hundred bucks when shipped to Europe...

[ChrisR]

I'm always surprised to find how difficult it is to tell whether the design is incuse or, um, excuse. The word should be excuse.

Splendid coin, looking glorious, you've done it proud.

[rjlittlefield]

I'm always surprised to find how difficult it is to tell whether the design is incuse or, um, excuse. The word should be excuse.

Is the entire design done in reversed depth, like the inside of a mask?

Or are the features of the head done in normal bas-relief, except that the whole head is sitting below the level of the surrounding coin?

--Rik

[colohank]

That's an interesting question, one that obliged me to dig out the coin for a closer look. The Indian Head is done in normal bas-relief but is recessed below the surface. Thus, the cheek and brow are higher in relief than the tip of the nose. The eagle motif on the other side of the coin is the same. Other features on both sides, the stars and date, motto, and denomination, etc., are simply stamped into the surface. Your query makes me wonder how the details might look under axial lighting if their topography were inverted.

[rjlittlefield]

Thanks for the further information.

Viewing flat with true axial lighting, the brightness as seen should depend on the magnitude of the surface slope but not its sign or direction. Having everything inverted would look fine in that special case.

However, with normal directional illumination inverting the depth would also invert the shadows. In that case actual light from above-left with inverted depth would be consistent with light from below-right with normal depth. Given the strength of our preconceptions about how heads are structured, I'm betting that the below-right interpretation would win out.

With coin in hand, turning it to catch the light in various ways, I'm guessing that inverted depth would just look confusing for a while, before the brain finally figured it out. Sort of like the rotating mask illusion.

--Rik

[ray_parkhurst]

Congrats to colohank for the award for this image. It's very nice, one of the better images I've seen using "axial" lighting. Fantastic coin as well, one of my favorites. Glad I saw the award post since I missed seeing this thread previously.