To calculate a long exposure time, you first measure the amount of light in your scene using the light meter in your camera or an external light meter. Then, you set the sliders under metered settings to the values the camera or light meter suggested. Next, set your preferred settings for the actual long exposure with the sliders under long exposure settings. Based on these values, Xpose calculates an appropriate exposure time for your long exposure shot. If you want to use a specific exposure time, you can tweak the other settings until the preferred exposure time is displayed.

Xpose was developed with HTML, CSS and JavaScript, and is hosted on GitHub Pages. You can read more on how it works, reciprocity failure, and the formulas used for each film stock on Xpose’s‎‎ information‎ page.