Calcedony?

Calcedony

This rock came from the bag I bought.  I thought it lovely primarily because of the yellowish coloration in the lower right.  I thought it added interest.

Calcedony Camera Setup

I wanted bottom light to accentuate the translucent quality of the yellow and white.  They were right at the edge of the piece so setting them on the light box was a built in solution.

At first, I used 1/60 and f/16, a reasonable place to start, but then I wondered if I could enhance the yellow by strengthening the bottom light.  The bottom light has only on/off control so I had to make the adjustment in camera.

Calcedony

The adjustment that I made was to increase the use of ambient light, that from the bottom.  I increased it from 1/60 to 3 seconds, about 7.5 stops.  The ec went from - 8.5 to -1.  fec did not change.  I think that you can see the change in the yellow.

Scale

I used a Sigma 105 mm lens with full set Kenko extension tubes, 68 mm.  This provides a 2.21 x on the sensor image.

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