I am an avid user of Long Exposure photography using up to 20 stops of filters. I have purchased and used EVERY iphone/ipad app made for calculating exposure times for specific filters/stacked filters and finally found Mario's app. It is by far easier and faster and more accurate then any I had found. This became my go to app. I loved it so much that I contacted Mario and begged him to make on for my MacBook Pro Retina as I use that on many of my location shoots. Well he did make it and released it yesterday. What a FANTASTIC app. Now I am covered on all my iPhones, iPads and now Macbook Pro. Thank you Mario!! You are a joy to communicate with and are the most helpful app developer I have come across.