Expo-Disc Expo Disc 58mm

The filter is, in effect, a gray card in a lens cap, letting photographers read and set white balance before shooting, eliminating the need for post-capture color adjustments. The filter works with film, digital cameras and digital video, and is available in six standard sizes from 58mm to 82 mm. The filter makes it possible to give the same, consistent white balance reference to an entire body of photographic work, allowing photographers to set white balance in mixed lighting conditions. The snap-on disc is a neutral diffusion filter that gathers ambient light from 180 degrees and passively transmits 18 percent of it through to the camera's light meter. The resulting "gray frame" accurately represents the colorcast of the light in which the photograph is being taken. From this gray frame, users can set a custom white balance with the digital camera's menu, resulting in accurate color in almost all lighting conditions. Each filter is manufactured and individually calibrated to fall within 1/12th f/stop accuracy for exposure.