Diamonds: Why “The Great Gatsby” Chose The Real Thing

(Inside Science) -- Being surrounded by expensive diamonds might sound like a woman’s dream come true, but according to “The Great Gatsby ” costume designer Catherine Martin, the choice to use real jewelry instead of fake had more to do with the cameras used for filming the movie than her taking a shine to the opportunity to rub elbows with millions of dollars’ worth of real diamonds and gemstones.

In the September 2012 issue of “Elle” magazine, Martin was asked why she decided to use fine jewelry during the filming of the movie instead of fake stones. Would the audience even notice? Martin replied, “The movie is in HD and 3D, so you can tell when a stone is real.”

This made me curious about the optical properties of real versus fake diamond as well as the challenges cinematographers face filming in HD and 3D. Would I, as a movie watcher and not a gemologist, really be able to tell the difference between a fake and a real diamond on screen? If what Martin says is true, I wanted to know how.

Since all that glitters may not be a real diamond, the refractive index is used to measure how a ray of light bends as it travels through an object. Real diamonds sparkle with a refractive index of 2.42, while cubic zirconia shimmers with a lower index of 1.18. Is the difference dramatic enough to be seen by the naked eye?

“If you’re an expert and you’re watching the movie, then yes, I believe you would be able to tell the difference between a real and a fake gemstone,” said Al Caudullo, a 3D filming expert at 3DGuy TV Productions. “As filmmakers our job is to strive for realism and just because most people aren’t experts doesn’t mean that we shouldn’t try to be as true to life as we can be.”

But even the use of real diamonds doesn’t solve all of a cameraperson’s challenges. “It is difficult to photograph and film diamonds,” said Maarten de Witte, a master diamond cutter and one of the founders of American Diamond Works. “From the lighting to using the right angle makes a difference.”

With my arms still unadorned, but my brain full of information, I wondered if perhaps Martin’s quote didn’t include the full scope of her impression. Maybe the selection of real diamonds for the film wasn’t really about the use of HD and 3D cameras at all. Perhaps the fake diamonds just didn’t look as brilliant on film when Martin looked at the footage from the camera tests, and realized that real diamonds were really the camera’s best friend.

Moviegoers can check out the film “The Great Gatsby” -- and the diamonds -- beginning tomorrow.