Updated Professional White-Balance Filter
The original ExpoDisc was an aluminum filter that you could mount on a lens for taking a white-balance measurement. ExpoImaging has released a new version of the ExpoDisc that has the same accuracy, but it comes in a more lightweight and cost-effective pack-age.
ExpoDisc 2.0 is a polycarbonate lens filter with two spring-loaded claws that grab the edge of the camera lens. (Initially, only the 77mm disc is available, but the company says that more sizes will follow.) On my camera, the claws grabbed the edges of the low-profile UV filter, but when I mounted it on a XUME magnetic filter holder, the filter turned out to be a fraction too small. There is a fix, however: Perhaps not as elegant, but equally efficient, is to hold the ExpoDisc 2.0 flush against the lens. The new mechanism works better than the tiny metal balls that held the first version in place.
What should appeal to most photographers is that one ExpoDisc 2.0 doesn't just take a white-balance measurement: It also functions as a portrait warm white-balancing tool. With the earlier ExpoDisc, you had to buy a separate warm white disc; with ExpoDisc 2.0, two warming gel filters are delivered with the disc. These are simple gels that you insert into the recesses on the face of the ExpoDisc 2.0. For each filter, two specially de-signed gels are included. That's just as well because, despite the snug fit, it probably wouldn't be hard to lose them. Backup gels are therefore not a luxury.
Hot:Â One disc for all white-balance settings; incident light meter capability
Not: Gels are more easily lost