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Thursday, August 24, 2006

Lighting Colored Gemstones

Doctor Charlie

My younger brother Charlie, who among other things is a mean cook, a decent guitar and piano player, an M.D. double-boarded in pediatrics and internal medicine who has his own practice, and a devoted dad, is also a gem cutter. He first learned to facet gems from a book when he was 14, and spent half of every day during his senior year in high school working at the Smithsonian Institution Gemology Department. He now has a nice little side-business called Technofacet, Ltd. selling beautifully faceted colored gemstones. (Very annoyingly, he makes more money doing this than I've ever earned at any of my main jobs. Sheesh—little brothers!) He owns one of the famously overengineered and overbuilt Gyro Gearloose faceting machines* (even though he seldom facets his own stones any more) and employs a network of some of the best freelance cutters in the world. Ironically, because he's a true "subject matter expert" and has no store overhead, his stones are of higher quality than most jewelry stores offer, and routinely appraise for 3X, or more, of what they sell for. Then again, it's not the world's easiest business. For instance, he refuses to keep any stones at his house, so everything he sells has to go by messenger from the safe deposit box at the bank to the Post Office. I suppose you get used to stuff like that, but if you thought organizing pictures was hard....

It turns out that photographing gemstones is a formidable specialty, and no trivial thing. Charlie tells me: "All of the photos for this week were taken by your eldest niece, with a 5MP Pentax Optio WP, using three halogen lights arranged right/left/over middle. The biggest problem in gem photography is the light—the stone is supposed to act like a retroreflector, so a truly ideally cut stone would show an image of your eye every time you look at it! Or, in this case, the camera (one reason we use a grey camera instead of my old black one)."

Back when I wrote more for magazines, I always meant to do an article on one or more of the grand master gem photographers, hoping to unearth some of the secrets of the skill. It's one of those projects I'll probably never get to. Still, any amateur who has ever tried to photograph a cut gemstone with his or her trusty macro lens can probably appreciate the surprising demands of the specialty.

Posted by: MIKE JOHNSTON
(Illustration: a 2.44 carat spectral chrome green tourmaline,
photograph by Christine Johnston)

* Note: the picture labeled "XS3 on a Graves" is Charlie's.

5 Comments:

Blogger Ken Tanaka said...

Charlie sounds like a real Renaissance man!

Indeed, photographing faceted gems is a real skill. It's one of those endeavors that seems like it would be easy. Bit it's one of photography's little hellpots to do well.

Tabletop Studio sells a variety of products to help light jewelry and other small objects for photography. (No doubt spawned by eBay's popularity.) They offer some tips on gem and jewelry photography that provides a good starting point for such projects.

3:35 PM  
Blogger pascal said...

I've done some gem photography for a gemstone class I taught a few years ago. Not only is lighting hard (I had some success with setting the gems on a light table for transmitted light and having several point sources of reflected light), but fingerprints show up too easily - archivists gloves are pretty much a must.

8:58 AM  
Anonymous Anonymous said...

Point your niece in the direction of the blog in general, and this particular post about lighting some highly-reflective spoons in particular.

The site is all about off-camera lighting, and the author, David Hobby, is a staff photographer for the Baltimore Sun. I have learned more about the actual practice of photography, even when using only ambient light, from Strobist over the past 4 months than I have from any other single source during the ~6 years I have actively pursued my interest in photography.

Norman

12:01 PM  
Blogger Rishi said...

Hi,

I'm a gemstone photographer and I have a question if anyone of you can help me out with that. Whenever I photograph green gemstones which are colored by chromium for example Emerald, Chrome Tourmaline, Tsavorite Garnet, Fluorite, etc. the color representation doesn't turn out to be accurate. It is either green with yellow hue or green with blue hue. But it is never the same rich green which is a perfect blend of blue, yellow and green. I suppose using a special filter should solve the purpose but I don't know which filter would be right for this. I photograph gemstones under white fluorescent lights and except for this color, all the colors turn out to be perfect. Kindly help. Thanks.

2:07 AM  
Blogger Mike Johnston said...

Rishi,
Our resident gemologist explains:

>>>
Thoughts - he's both correct and screwed.

Chromium is an interesting chromophore - it is responsible for the red in Ruby, the green in Emerald, and BOTH in Alexandrite. It is very sensitive to the color of the light - Alexandrite looks like a Ruby under incandescent and like an Emerald outdoors (good ones are really freaky, but also really rare). It also fluoresces, which further complicates things (but which is responsible for the famous "glowing coal" appearance of some Rubies - Iron impurities quench the fluorescence, so iron containing rubies like Thai and most Sri Lankan do not "glow").

I have the same problem, which seems to be CCD related. Regardless of color balancing, chromium containing gems appear bluish on the Pentax CCDs and yellowish on Nikon.

Other than manipulation of the image afterwards, I know of no way to correct for this.

Cheers,

-C.
<<<

10:36 AM  

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