Field Test: Expodisc

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In 1980, the world of photography was a very different place. Film was the undisputed medium and photography's elder statesman Ansel Adams was still alive. Those who discussed pixels, color space and resolution were typically PhD's who were working for R&D facilities or the military. Outside of shooting Polaroids, the average photographer couldn't fathom the ability to shoot and instantly see the results as a high resolution, full color image.

Back In 1980, George Wallace was one of those photographers, and he had an idea. An avid fan of Ansel Adams and the zone system, Wallace dreamed of making a device that would work as a simple converter -- making the average camera and lens into an incident meter. Little did Wallace know that years later, his idea would start a revolution in the field of digital imaging by making a product that balances color nearly perfectly each time it's used.

Wallace died in 2001, never seeing his invention come to its full modern fruition. His daughter, Diane Wallace, who is an art historian and amateur photographer, wanted to see his invention grow, and in a chance conversation with a forum of photographers, Wallace realized that what her father had invented was more useful to digital photographers than film-based zone system enthusiasts. So, Wallace and her family began the process of refining the disc for the digital age.

"He had a lathe on the porch in the back of his house. Back then, it took about 30 minutes to make one disc and they were completely hand made," explains Eric Sowder, Wallace's grandson and the President of ExpoDisc. "We have refined the process twice since then, but basically the discs are still hand made..."

Hand made, but at an extremely high level of precision. The tolerances for correct color are within 1 percent on each disc the company manufactures, which range in price from $80 to $200. This level of precision becomes obvious when you open your ExpoDisc box and see that little card with the densitometry readings for the disc you're holding. While the density readings have no real bearing on the disc and your use of it, it does drive the point home that this is a high precision device and suddenly, it becomes obvious why the disc is a little more expensive in comparison to an average filter or cardboard gray card.

"The secret is between the acrylic elements" Sowder explains. "We take a color measurement through the materials and compensate for it to ensure that it is perfectly neutral." The results are a disc that acts like a gray card, yet doesn't bend, fade, crease or otherwise become a hassle to carry with you and use effectively. The ExpoDisc comes in a variety of sizes and also features a "Warming" version that is targeted at portrait photographers because it adds more green/blue into the filter itself, therefore giving the overall corrected image a greater red/yellow bias, which should add subtle overall warmth to skin tones.

The idea behind the disc is also quite simple. By covering your favorite lens with the ExpoDisc and pointing it at the light source for your images and giving the frame a correct exposure, you'll create a perfect 18 percent reflective "gray frame." There are however different ways that the ExpoDisc can be used, and I found that the simplest (and preferred method by ExpoDisc) is to make a custom white balance using the disc over the lens. The results are consistent on my calibrated monitor, and resembled the color of the scene that I recalled in comparison to the other white balance settings I used. In short, the ExpoDisc is an amazingly simple way to save yourself an endless amount of time correcting color -- particularly if you have a large group of images that will be shot under identical lighting conditions.

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