NDTimer is an iPhone app developed by Threesixty Digital Design Co. that is designed to assist photographers and videographers in calculating and timing long exposures when using one or two neutral density (ND) filters. The app is available as a full version and falls under the multimedia category.

The app's interface is straightforward and user-friendly. It allows users to input their desired exposure time, the strength of their ND filter, and the number of filters they are using. The app then calculates the correct shutter speed needed and provides a countdown timer to assist with timing the exposure. Additionally, the app includes a handy reference chart for common ND filter strengths and their corresponding stops of light reduction.

Overall, NDTimer is a useful tool for any photographer or videographer looking to achieve long exposures with ND filters. Its simple interface and accurate calculations make it a valuable addition to any photographer's toolkit.