In this Photofocus blog post I share my experience with an app designed to calculate exposure time when using a neutral density filter. I love long exposure photography because it has the power to make even the most mundane scenes a bit more interesting visually. When shooting daytime scenes I often turn to my Lee Big Stopper 10-stop ND filter. The Big Stopper is so dark you can’t actually see through it, which means your camera’s internal metering is off the table. Lee does include a small cheat sheet with the filter to help you determine the correct exposure with the ND filter based on the correct exposure without the filter. Unfortunately the cheat sheet doesn’t cover all possible exposure values, so you are left to doing the calculations in your head, just guessing, or using some other calculator. Plus to be honest, I lost that cheat sheet a long time ago. Continue reading at Photofocus.com.