I have since experimented with both my camera and with my photo imaging
software, and I've smoothed the way to use High Dynamic Range (HDR) on all
types of
ancient coins, silver, gold, and bronze. My
collection of third and fourth century
Roman coins is a medley of metals, and a
good testbed.
Below are examples of automated merging of photos of gold and bronze coins using "bracketed" shots from the camera and HDR processing in PC
software. All photos are unretouched here.
The camera has several settings that, when used in combination, allow me to shoot three photos at different exposures with a single press of the shutter button. KISS.
The
software has a batch mode that allows me to take my usual complement of a dozen coins and, with a single command, photomerge the 72 photos (3 each of the
obverse and
reverse) into twelve pairs of HDR photos. I find the effect to be stunning.
I'm shooting everything using axial lighting, bouncing LED light off clear
glass, with some additional soft direct lighting. The rather diffused glow doesn't make for deep shadows anywhere, so features like legends do not tend to stand out much. The HDR seems to
help increase detail, compensating for the flatness that
comes with the axial lighting. Congius manages to use
side lighting effectively, so there's clearly more than one way to overcome bright reflections.