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ExpoDisc is the easiest way to use the Custom Color function on your digital camera. This combination makes it easy to capture accurate color, even in tricky lighting conditions. I've covered the basics in a previous article titled ExpoDisc for Pro (and Easy) Color Capture. But according to color expert Bill Atkinson, there's more to this handy photo accessory than initially meets the eye.

I learned about Bill's thoughts while in Iceland on the Lightroom Adventure. During a group dinner, we discussed how to use the ExpoDisc in the field to help us capture accurate color. At the time, I didn't know that Bill had tested the device. But after a few minutes of discussion, I discovered that he knew more about this product than anyone else in the room.

Fortunately we had a video camera there, and we were able to record this snippet where Bill not only talks about the standard uses for the ExpoDisc, but more advanced functions, too, such as dust mapping.

Bill Atkinson describes advanced uses for the ExpoDisc

To watch Bill Atkinson describe advanced uses for the ExpoDisc, click here.

He began by comparing the ExpoDisc to a standard gray card. In even lighting, Bill said that the ExpoDisc provides similar results to the card, but it's much more compact and durable. But in odd lighting, the image capture often differs between the two methods, and he almost always likes the results from the ExpoDisc better.

That night, I thought he explained the basic use of the device as well as anyone I had heard previously. I certainly was glad to have his thoughts on tape. But then things took an unexpected turn. Bill said that you can use the ExpoDisc to analyze color shift across your image sensor, so if it leans toward magenta on one side and green on the other, you can see that.

The really interesting tip, however, is stopping down your lens aperture to f-22, recording a frame with the ExpoDisc, and then looking at the image on your computer to see if there was any sensor dust. Bill went on to say that you could even use this "dust map" to clean up images from the same shoot in post production.

The video runs 2:04 and requires a current version of QuickTime or iTunes for playback. You can even watch it on your 5th Gen iPod if you want to view the movie on the go.

Video captured by Chris Sanderson.

Derrick Story is the author of The Photoshop CS4 Companion for Photographers, The Digital Photography Companion, and Digital Photography Hacks, and coauthor of iPhoto: The Missing Manual, with David Pogue. You can follow him on Twitter or visit www.thedigitalstory.com.


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